DESC:FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)

TITLE OF THE INVENTION:
SYSTEM AND METHOD FOR ANALYSIS OF ASPHALTENE OR OTHER SCALE-FORMING DEPOSITION IN PIPELINES

APPLICANT:
Name: Tridiagonal Solutions Pvt. Ltd.
Nationality: Indian
Address: Tridiagonal Solutions Pvt. Ltd., Plexus, 3rd Floor, ITI Road, Aundh, Pune 411007, India

PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

This is a complete specification filed in respect of provisional application having no. 202221035421 filed on 21st June, 2022.
A) TECHNICAL FIELD OF INVENTION
[001] The present invention generally relates to monitoring, detection and analysis of impurities deposition in the pipelines and particularly relates to the deposition of asphaltene and other scale forming depositions in the pipelines. The present invention more particularly relates to the system and method of monitoring and analysis of the asphaltene and other depositions in tubular pipelines under various flow regimes.

B) BACKGROUND OF INVENTION
[002] Scale deposition can be defined as the aggregation of different materials within unwanted parts/areas in the oil/gas production system, one of which is the asphaltene deposition. The issue of asphaltene deposition has plagued the oil and gas industry for decades. Crude oil has several fractions such as asphaltenes, waxes including paraffins, hydrates and scale, etc. among others. Among all these, asphaltenes essentially tend to be its heaviest and least soluble fractions. They are known as the “cholesterol of petroleum” due to their ability to precipitate as solids and subsequently deposit with changing pressure, temperature, and oil composition. This may affect both surface properties and crude oil rheology.
[003] In both upstream and downstream operations, these depositions cause severe problems such as they get deposited on the pipeline surfaces, bottom of distillation columns and in heat exchangers as well, affecting efficiency and creating added economic costs to remediate. Deposition can lead to fouling and/or damage during oil production or refining. During crude oil production, they can deposit in reservoir rock pores, thus leading to possible blocking of flow, particularly in the near well bore region.
[004] Asphaltenes are present in crude oil as stable sub-micron sized colloidal suspensions. Changes in the oil such as temperature, pressure or composition can cause these colloidal particles to self-associate or flocculate thereby forming larger particles. When these particle aggregates become large enough, they can settle out of the oil, or precipitate as a loose solid material. When the asphaltenes adhere to the walls of the pipe or vessel, this process is referred to as deposition which is distinct from precipitation.
[005] The stabilization of asphaltene particles is sometimes disturbed due to various factors like a reduction in pressure, and changes in temperature and composition. Destabilization of asphaltene particles causes deposition of these solid flocs of asphaltene from the crude oil onto the interior surfaces of the pipes. However, when deposition in a pipe occurs, it is generally undesirable because deposited solids can at least partially block the pipe and lead to reduction in the flow rate of the fluid in the pipe and require expensive and time-consuming cleaning of the pipe to restore the maximum or minimum acceptable flow rate of the fluid.
[006] Similar to the deposition of asphaltenes, other pipeline deposits are known to form in petroleum pipelines under the influence of changes in temperature, pressure, or composition. Pipeline scale formation occurs when water with dissolved solids forms precipitates and deposits. For example, water containing dissolved calcium salts (also called hard water) can form Calcium Carbonate (CaCO3) deposits. Calcium Carbonate scale formation is commonly encountered in boilers and hot water heaters. Deposits of dissolved solids are called pipeline scale. Another such scale-forming material is Barium Sulfate (BaSO4). Barium Sulfate deposits commonly form when water is produced and combined from various geologic formations.
[007] When scale-forming solids precipitate, they can be carried along with the water or deposit on the inside of the pipeline. Various chemicals called scale inhibitors are used in an attempt to allow precipitation but to prevent scale formation or deposition. There is a need to be able to test these both the scale forming waters and the scale inhibitors under actual turbulent pipe flow conditions to determine their scale forming tendencies.
[008] In the past, various chemicals such as asphaltene inhibitors are sometimes used in pipelines to reduce the rate of deposition of asphaltene particles in the pipelines. The efficiency of these inhibitors depends on several factors such as selection of the right chemical, amount of injection, introduction of chemical inhibitor at the correct location in pipeline and targeting of the right operating conditions, etc. Bench-scale or lab-scale testing has been used in past to screen out and measure the efficiency of the various chemical inhibitors.
[009] There have been prior arts which disclose use of bench-scale tests such as shear deposition cells or capillary tubes for studying asphaltene deposition, quantitatively. However, they don’t mimic the actual conditions of pipelines in oil & gas wells. For turbulent flow conditions, mostly a shear deposition cell is selected for studying asphaltene deposition as no other economical design or apparatus is available to study deposition behaviour under these conditions. A required amount of shear is created in the cell similar to that of pipelines under turbulent flow but this setup is unable to properly imitate real pipelines due to differences in the flow profile and flow behaviour inside the cell compared to a pipe flow. Hence, researchers preferably use capillary tubes to study the deposition behaviour of asphaltene. These capillary tubes are very small in diameter (around 0.02 inches) as compared to the pipelines that are used in the oil and gas industry (around 4 inches or more). Capillary tubes have the advantage of allowing tests using small amounts of oil but capillary tubes are restricted to laminar flow. Hence, studying the asphaltene deposition by mimicking similar flow behaviour in the crude oil pipelines is a big challenge.
[0010] In view of the foregoing, there is a need to develop a simple and economical apparatus and an improved method for evaluating asphaltene and other scale forming depositions in the pipelines that simulate real flow behaviour of liquids inside pipelines under a range of flow conditions while also using attainable amounts of oil for the tests. There is also a need to develop a simulation test apparatus that maintains turbulent flow of liquids inside a pipe flow geometry while using low injection rate of oil.
[0011] The value additions and above-mentioned shortcomings, disadvantages and problems are addressed herein, as detailed below.

C) OBJECT OF INVENTION
[0012] Thus, the primary object of the present invention is to provide a method and system for the analysis of asphaltene or other scale forming depositions in the pipelines.
[0013] Another object of the present invention is to provide an apparatus/system for evaluating crude oil asphaltene deposition or other scale forming depositions, especially a turbulent flow generating simulation test apparatus.
[0014] Yet another object of the present invention is to provide an improved method for evaluating asphaltene or other scale forming depositions in crude oil pipelines and likewise.
[0015] Yet another object of the present invention is to provide a simulation test apparatus/system for evaluating crude oil asphaltene or other scale forming depositions wherein the test apparatus/system maintains a turbulent flow of liquids inside the pipelines at low injection rate.
[0016] Yet another object of the present invention is to provide a simulation test apparatus/system for evaluating crude oil asphaltene or other scale forming deposition wherein the test apparatus/system provides a long residence time of liquids inside the pipelines for the asphaltene particles to deposit.
[0017] Yet another object of the present invention is to provide a simulation test apparatus/system for evaluating crude oil asphaltene or other scale forming depositions having pipelines with larger diameter to simulate real flow behaviour of liquids inside pipelines.
[0018] Yet another object of the present invention is to provide a simulation test apparatus/system for evaluating crude oil asphaltene or other scale forming depositions that is simple, efficient and economical to make.
[0019] Yet another object of the present invention is to provide a method for evaluating crude oil asphaltene or other scale forming depositions wherein the operational cost for carrying out analysis of asphaltene deposition in pipelines is economical.
[0020] Yet another object of the present invention is to provide a method and apparatus for evaluating other depositional behaviour such as water scale formation (CaCO3, BaSO4) under turbulent pipe flow conditions.
[0021] These and other objects and advantages of the embodiments herein will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

D) SUMMARY OF INVENTION
[0022] According to an embodiment of the present invention, a system and method for analysis of asphaltene or other scale-forming deposition in pipelines is provided. The system is a high turbulence generating simulation test apparatus for evaluating asphaltene or other scale-forming depositions.
[0023] The system 100 for analysis of asphaltene or other scale-forming deposition in pipelines comprises a pair of tank assembly, wherein one tank assembly is a test fluid tank assembly 1 and another tank assembly is precipitant tank assembly 7, at least two low flow rate pumps 6 and 10, a plurality of flow controlling units 3 and 8, at least two flow meters 4 and 9, at least two inlet streams 12 and 13, a plurality of connecting pipelines ‘P1’, ‘P2’ and ‘P7’, a plurality of shut off valves 5, 17, and 16, a plurality of check valves 11, and 35, a pressure regulator 18, a circulating Test Rig 14 and a waste drum 19.
[0024] According to an embodiment of the present invention, the temperature transmitter 2 is attached to the test fluid tank assembly 1.
[0025] According to an embodiment of the present invention, the connecting pipeline ‘P1’ is present between test fluid tank assembly 1 and circulating Test Rig 14, wherein the connecting pipeline ‘P2’ is present between is precipitant tank assembly 7 and circulating test rig14, wherein the connecting pipeline ‘P7’ is present between the circulating test rig 14 and the waste drum 19.
[0026] According to an embodiment of the present invention, the inlet stream 12 is present between the test fluid tank assembly 1 and circulating Test Rig 14.
[0027] According to an embodiment of the present invention, the inlet stream 13 is present between the precipitant tank assembly 7 and circulating Test Rig 14.
[0028] According to an embodiment of the present invention, the diameter of the connecting pipelines ‘P1’, ‘P2’ and ‘P7’ is less than 1 inch.
[0029] According to an embodiment of the present invention, the circulating test rig 14 forms a ‘4-limbed’ shaped closed test rig system with 3-diameter (or greater) curvature elbows 21, 24, 31, 34 at the bending points.
[0030] According to an embodiment of the present invention, the circulating Test Rig 14 further comprises a high flow rate pump 26, a non-return valve 27, a mass flow meter 28, a flow controlling unit 33, at least four connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6’, at least four bending points 21, 24, 31, 34, a plurality of temperature transmitters 22, 29 32, and 41, a plurality of pressure transducers 23, 30, 39, and 40, a spool piece 38, a discharge point 15, at least two pipelines ‘P8’, ‘P9’, a pressure safety valve (psv) 36, a vent port 37, and a drainage port 20.
[0031] According to an embodiment of the present invention, the high flow rate pump 26 and the flow controlling unit 33 is present on the connecting pipeline ‘P6’.
[0032] According to an embodiment of the present invention, the non-return valve 27 is present at the discharge of the high flow rate pump 26.
[0033] According to an embodiment of the present invention, the mass flow meter 28 is present succeeding to the non-return valve 27 on the connecting pipeline ‘P6’.
[0034] According to an embodiment of the present invention, discharge point 15 is present on the connecting pipeline ‘P5’.
[0035] According to an embodiment of the present invention, the spool piece 38 is present on the connecting pipeline ‘P4’.
[0036] According to an embodiment of the present invention, the flow is unidirectional.
[0037] According to an embodiment of the present invention, the diameter of the connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6’ is greater than or equal to 1 inch.
[0038] According to an embodiment of the present invention, the length of one or more of the connecting pipelines ‘P3’, ‘P4’, and ‘P5’ is greater than 10 diameters. According to an embodiment of the present invention, the system maintains a high residence time of greater than 50 minutes inside the pipelines while capable of achieving a higher shear stress on the walls of pipeline.
[0039] According to another embodiment of the present invention, a method for analysis of asphaltene or other scale-forming deposition in pipelines comprises:
(a) filling a tank assembly 1 with a test fluid and a tank assembly 7 with a precipitant;
(b) injecting a test fluid in a connecting pipeline ‘P1’ through a low flow rate & high discharge pressure pump 6;
(c) injecting the precipitant in a connecting pipeline ‘P2’ through a low flow rate & high discharge pressure pump 10;
(d) filling a test rig 14 with a continuous injection of the test fluid and the precipitant through connections ports 12 and 13;
(e) maintaining a desired temperature inside the Test rig 14 using external heat tracers to the pipelines P3, P4, P5, P6;
(f) setting a desired pressure at which a deposition studies need to be carried out in Test Rig 14 using a pressure regulator 18 placed in the pipeline P7;
(g) turning on a pump 26 and maintaining a desired circulation flow rate in Test Rig 14;
(h) carrying out deposition test for a particular time duration and recording all the desired parameters;
(i) draining out the liquid mixture after completion of the deposition test using drainage port 20, and collecting solids deposition from test fluid & precipitant mixture by solvent washing; and
(j) determining the actual solid content.
[0040] According to an embodiment of the present invention, the precipitant is n-alkane for precipitating asphaltene from crude oil while a known precipitating aqueous solution for other test fluids like hard water or formation water.
[0041] According to an embodiment of the present invention, the method is used for determining chemical species such as calcium carbonate, barium sulfate that precipitates from a liquid and deposit on the pipe walls.
[0042] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

E) BRIEF DESCRIPTION OF DRAWINGS
[0043] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0044] FIG. 1 is a schematic showing the system 100 for analysis of asphaltene or other scale-forming depositions in pipelines, according to an embodiment of the present invention.
[0045] FIG. 2 is schematic showing the circulating Test Rig 14, according to an embodiment of the present invention.
[0046] FIG. 3 is a flow chart showing the various steps involved in the method of for analysis of asphaltene or other scale-forming depositions in pipelines, according to an embodiment of the present invention.

F) DETAILED DESCRIPTION OF EMBODIMENTS
[0047] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. The embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical, electronic and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0048] The various embodiments of the present invention provide a system for evaluating test fluid (crude oil or formation water) solid deposition, especially the high turbulence generating simulation test apparatus. The present invention provides an advanced system and improved method for evaluating solid deposition in test fluid pipelines or likewise, wherein the apparatus maintains a turbulent flow of liquids inside the pipelines at a low injection rate of liquids while maintaining sufficient residence time for particles to deposit on pipelines.
[0049] According to an embodiment of the present invention, the system comprises a unique close loop type structure which regulates the flow of liquid and deposits asphaltene or other solids which can be measured easily. The present invention is designed in a way that it creates turbulence inside the pipelines where the asphaltene or other scale-forming deposition studies can be done.
[0050] The present invention is designed in such a way that it maintains a high residence time (up to 50 minutes or more) of liquids inside a unique close loop of pipelines while also achieving a high shear stress on the pipe walls. Further, the present invention uses a large enough diameter of the pipe (up to 1 inch or more) which provides real laminar, transitional, or turbulent pipe flow behaviour. Furthermore, the present invention uses a limited amount of test fluid for deposition studies as compared to conventional practices which require huge volumes of oil for maintaining turbulent flow and high residence time in pipelines.
[0051] According to an embodiment of the present invention, a system for evaluating solid (asphaltene, CaCO3, or BaSO4) deposition mainly comprises a pair of tank assemblies, flow rate pumps, flow meters, flow controlling units and closed circulating loop with connecting pipelines. The system of the present invention enables solid deposition studies to be performed under various flow regimes while using precipitant such as n-alkane or any other precipitating aqueous solution as solid precipitator to produce scale-forming particles such as asphaltene, CaCO3, or BaSO4 inside pipelines.
[0052] The present invention relates to both a system and process design with an objective to analyse the depositional behaviour of asphaltene or other scale forming particles in pipelines under various flow conditions by maintaining a sufficient amount of residence time for the particles to deposit.
[0053] With respect to FIG. 1 & FIG. 2, a high turbulence generating simulation test apparatus for evaluating test-fluid solid deposition is provided. The simulation test apparatus 100 for evaluating test-fluid solid deposition, comprises: a pair of tank assemblies, wherein one tank assembly is test fluid tank assembly 1 and another tank assembly is precipitant tank assembly 7, at least two low flow rate pumps 6 and 10, a plurality of flow controlling units 3, and 8 at least two flow meters 4 and 9, at least two inlet streams 12 and 13, a plurality of connecting pipelines ‘P1’, ‘P2’ and ‘P7’, a plurality of shut off valves 5, 17, and 16, a plurality of check valves 11, and 35, a pressure regulator 18, a circulating Test Rig 14 and a waste drum 19.
[0054] According to an embodiment of the present invention, a temperature transmitter 2 is attached to the test fluid tank assembly 1. The temperature of the test fluid inside the pipeline is monitored using the temperature transmitter 2 attached to the test fluid tank assembly 1.
[0055] According to an embodiment of the present invention, the test fluid tank assembly 1 is connected to the low flow rate and high discharge pressure pump 6. The continuous flow of the test fluid is maintained into the circulating Test Rig 14 using pump 6.
[0056] According to an embodiment of the present invention, pump 6 is a low flow rate and high discharge pressure pump. The pump 6 can be syringe pumps or HPLC pumps.
[0057] According to an embodiment of the present invention, pump 6 is connected to the flow controlling unit 3. The flow controlling unit 3 controls the flow of the test fluid from the tank assembly 1 to the circulating Test Rig 14.
[0058] According to an embodiment of the present invention, flow meter 4 is placed on the upstream side of pump 6. The flow meter 4 measure the flow rate or the injection rate of the test fluid from pipeline ‘P1’ into the circulating loop process 14.
[0059] According to an embodiment of the present invention, the pipeline ‘P1’ is present between test fluid tank assembly 1 and circulating Test Rig 14. The test fluid is pumped into the circulating Test Rig 14 via connecting pipeline ‘P1’.
[0060] According to an embodiment of the present invention, shut-off valve 5 and check valve 11 are present on the connecting pipeline ‘P1’.
[0061] According to an embodiment of the present invention, the inlet stream 12 is present between the test fluid tank assembly 1 and circulating Test Rig 14. The test fluid enters into the circulating test rig 14 as the inlet stream 12.
[0062] According to an embodiment of the present invention, the precipitant tank assembly 7 is connected to the pump 10. The continuous flow of the n-alkane is maintained into the circulating Test Rig 14 using the pump 10.
[0063] According to an embodiment of the present invention, the pump 10 is a low flow rate and high discharge pressure pump. The pump 10 can be syringe pumps or HPLC pumps.
[0064] According to an embodiment of the present invention, pump 10 is connected to the flow controlling unit 8. The flow controlling unit 8 controls the flow of precipitant from the tank assembly 7 to the circulating Test Rig 14.
[0065] According to an embodiment of the present invention, the flow meter 9 is placed on the upstream side of pump 10. The flow meter 9 measure the flow rate or the injection rate of the precipitant from the pipeline ‘P2’ into the circulating Test Rig 14.
[0066] According to an embodiment of the present invention, the pipeline ‘P2’ is present between is precipitant tank assembly 7 and the circulating Test Rig 14. The precipitant is pumped into the circulating loop Test Rig v14 via connecting pipeline ‘P2’.
[0067] According to an embodiment of the present invention, the shut-off valve 17 and check valve 35 are present on the connecting pipeline ‘P2’.
[0068] According to an embodiment of the present invention, the inlet stream 13 is present between the precipitant tank assembly 7 and circulating loop test rig 14. The precipitant enters into the circulating test rig 14 from the inlet stream 13.
[0069] According to an embodiment of the present invention, the test fluid and the precipitant is pumped from the test fluid tank 1 and precipitant tank assembly 7, respectively using low flow rate and high discharge pressure pumps 6 and 10 to maintain continuous flow of liquids inside the circulating Test Rig 14.
[0070] According to an embodiment of the present invention, the circulating Test Rig 14 forms a ‘4-limbed’ shaped closed loop system with 3-diameter (or greater) curvature elbows 21, 24, 31, 34 at the bending points of pipelines.
[0071] According to an embodiment of the present invention, to achieve a turbulent flow as well as a high residence time of liquid inside the pipelines, the circulating test rig comprising of circulating connecting pipelines and the high flow rate pump is provided. A continuous injection and discharge to the circulating test rig is maintained using other low flow rate pumps. This allows achieving a turbulent flow of liquids inside the pipelines while generating a higher shear on the walls as well as a high residence time of liquids inside the process even at a low injection rate of liquids. The injection rate of liquids in the circulating test rig varies from 1 to 120 ml/min, approximately.
[0072] According to an embodiment of the present invention, the circulating Test Rig 14 further comprises a high flow rate pump 26, a non-return valve 27, a mass flow meter 28, a flow controlling unit 33, at least four connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6’, a plurality of temperature transmitters 22, 29, 32 and 41, a plurality of pressure transducers 23, 30, 39 and 40, a spool piece 38, a discharge point 15, at least two pipelines ‘P8’, ‘P9’, a pressure safety valve (psv) 36, a vent port 37, and a discharge port 20.
[0073] According to an embodiment of the present invention, the test fluid and the precipitant gets mixed in the connecting pipelines of the circulating Test Rig 14. The mixture of test fluid and precipitant flows inside the connecting pipelines P3’, ‘P4’, ‘P5’ and ‘P6’of the circulating Test Rig 14.
[0074] According to an embodiment of the present invention, a high flow rate pump 26 and a flow controlling unit 33 is present on connecting pipeline ‘P6’.
[0075] According to an embodiment of the present invention, the non-return valve 27 is present at the discharge of the pump 26. The non-return valve or check valve 27 prevents the back flow of the mixture of test fluid and precipitant through the pump 26.
[0076] According to an embodiment of the present invention, pump 26 is a high flow rate pump. The high flow rate pump 26 maintains the turbulent flow of mixture of test fluid and precipitant in the circulating Test Rig 14. The mixing of crude-oil or other test fluid and precipitant in the circulating Test Rig 14 enables precipitation followed by deposition of asphaltene or other scale-forming deposits in pipelines. The high flow rate pump 26 is capable of handling higher pressure both at its suction and discharge side. This enables Test Rig 14 to be able to operate at high pressures. However, the same Test Rig 14 is capable of maintaining a low flow rate inside the pipes which enables it to carry out deposition studies in the laminar region.
[0077] According to an embodiment of the present invention, a mass flow meter 28 is present succeeding to the non-return valve 27 on the connecting pipeline ‘P6’.
[0078] According to an embodiment of the present invention, discharge point 15 is present on the connecting pipeline ‘P5’. The total flow rate i.e., the sum of the flow rate of test fluid and precipitant that is injected is withdrawn at discharge point 15 for maintaining a constant amount of the mixture inside the Test Rig 14.
[0079] According to an embodiment of the present invention, the spool piece 38 is present on the connecting pipeline ‘P4’. The overall circulating pipelines except spool piece 38 are coated with inhibitor to avoid deposition of asphaltene or other solid particles. Therefore, spool piece 38 becomes the test specimen where deposition of particles takes place. After completion of test, spool piece 38 is removed from the pipeline P4. The spool piece 38 is subjected to solvent washing to remove the deposition of solids. The solution is subjected to vaporization to remove solvent and the residue is collected. Generally, the residue in case of crude oil as test fluid contain wax, asphaltene, and inorganic particle. The residue is subjected to analysis using ASTM D6560 methods for determining actual asphaltene deposition. Similarly, known analytical methods is selected for analysis of other scale-forming deposits. However, present invention is flexible in carrying out deposition studies in overall test rig 14 as well as in a specific location of test rig 14.
[0080] According to an embodiment of the present invention, the flow is unidirectional.
[0081] According to an embodiment of the present invention, the diameter of the connecting pipelines P3’, ‘P4’, ‘P5’ and ‘P6’is greater than or equal to 1 inch.
[0082] According to an embodiment of the present invention, the pipeline ‘P7’ is present between Test Rig 14 and the waste drum 19. The discharged liquid is collected in the waste drum 19.
[0083] According to an embodiment of the present invention, the shut-off valve 16 and a pressure regulator 18 are present on the connecting pipeline ‘P7’.
[0084] According to an embodiment of the present invention, the diameter of pipelines ‘P1’, ‘P2’ and ‘P7’ is less than 1 inch.
[0085] The system of the present invention maintains a high residence time of 50 minutes or greater inside the pipelines while achieving higher shear stress on the walls of pipeline.
[0086] According to an embodiment of the present invention, the test fluid flows from the tank assembly 1 and precipitant flows from the tank assembly 7 to circulating test rig 14. The test fluid and the precipitant get mixed and flows through the connecting pipelines of the circulating test rig 14. Here, the desired flow rate is maintained and deposition of asphaltene or other scale-forming particles is carried out in pipelines. Continuous injection of both test fluid and precipitant into test rig 14 is carried out using pipelines P1 & P2 while a discharge of the same volume of mixture is done using pressure regulator 18 present in pipeline P7 to the waste drum 19.
[0087] FIG. 3 is a flow chart showing the various steps involved in the method for analysis of asphaltene or other scale-forming deposition in pipelines, according to an embodiment of the present invention. With respect to FIG. 3, the method comprises filling a tank assembly 1 with test fluid such as crude oil or formation water and tank assembly 7 with precipitant such as n-alkane or precipitating aqueous solution (a), respectively. The test fluid is injected in connecting pipeline ‘P1’ through low flow rate & high discharge pressure pump 6 (b). The precipitant is injected in connecting pipeline ‘P2’ through low flow rate & high discharge pressure pump 10 (c). The test fluid and precipitant are filled into the circulating Test Rig 14 through connections ports 12 and 13 (d). A desired temperature is maintained inside the Test rig 14 using external heat tracers to the pipelines P3, P4, P5, P6 (e). A desired pressure is set at which a deposition studies need to be carried out in Test Rig 14 using a pressure regulator 18 placed in the pipeline P7 (f). A pump 26 is turned ON and a desired circulation flow rate is maintained in Test Rig 14 (g). A deposition test for a particular time duration is carried out and all the desired parameters are recorded (h). The liquid mixture is drained out after completion of the deposition test using drainage port 20 and solids deposition is collected from the test fluid & precipitant mixture by solvent washing (i). The actual solid content is determined (j).
[0088] Once the Test Rig 14 is filled with mixture of test fluid and precipitant and certain pressure is maintained in the test rig using a pressure regulator 18 placed in pipeline P7. As continuous injection of both test fluid and precipitant continues, to avoid increase in the pressure of the Test Rig 14 the excess mixture is released by the pressure regulator 18 to maintain a constant pressure inside the Test Rig 14. Once a stable state is achieved in the Test Rig 14 i.e. the combined injection rate remains the same as discharge rate, pump 26 is turned on and a desired flow rate of mixture is achieved inside the Test Rig 14. The deposition studies are carried out for a desired time duration by maintaining a constant temperature of the mixture inside the Test Rig 14. After the completion of deposition test, the liquids are drained at drainage port 20 at test pressure. If deposition is carried out in overall loop, then solvent is injected into the Test Rig through the pipeline P2 by taking another port. The deposits are recovered by mixing with solvent which is followed by collecting solvent mixture and evaporating solvent to get deposits. These deposits/solids are analyzed using ASTM D6560 (for asphaltene) or other known methods to get actual asphaltene or other particle content that has been deposited on the overall test rig. If deposition is carried out only in a specific location like spool piece 38 (other locations are coated with inhibitor for avoiding depositions), then spool piece 38 is removed from the Test Rig 14 and this is followed by recovering deposits through solvent washing and evaporating the solvent to get deposits. These deposits are analyzed using ASTM D6560 methods (for asphaltene) or other known analytical methods to get actual solid (asphaltene or other particles) content that has been deposited on a specific location like a spool piece 38.
[0089] According to an embodiment of the present invention, the working principle of the test simulation apparatus 100 of the present invention is provided by first filling tank assembly 1 with test fluid such as crude oil or formation water and the tank assembly 7 with precipitant such as n-alkane or precipitating aqueous solution. After filling the test fluid and precipitant in the circulating test rig 14, continuous injection of both test fluid and precipitant is carried out at the inlet streams or points 12 and 13 using the low flow rate pumps 6 & 10. At the same time, a total flow rate i.e. the sum of the flow rate of test fluid and precipitant that is injected is withdrawn at discharge point 15 for maintaining a constant amount of the mixture inside the circulating test rig 14. The high flow rate pump 26 is turned “ON” to create the desired turbulence or Reynold’s number inside the circulating test rig 14 along with proper mixing of test fluid with precipitant. This leads to the precipitation of solid particles from the test fluid followed by the deposition of solid particles on the inner walls of the connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6 of the circulating test rig 14.
[0090] According to an embodiment of the present invention, when we increase the Reynolds number the flow regime changes from laminar to turbulent flow which causes the pressure drop in Test Rig 14 to increase. The pump 26 is capable of giving a higher differential pressure of 10 bar which is sufficient for the fluid to overcome pressure drop over the Test Rig 14 up to a Reynolds number of 30,000. However, the present invention provides a test rig above 10 bar which means a deposition test at high pressures greater than 10 bar can be conducted. The same invention can be used at a low pressure of below 10 bar when the pressure drop of Test Rig 14 is low or below 10 bar.
[0091] According to an embodiment of the present invention, once the liquids are filled inside Test Rig 14, the desired flow rate is set using flow controlling unit 33 to achieve the required flow regime (laminar, turbulent). The present invention is not limited to only turbulent flow as it can be used for low flow rate regimes like laminar or transition.
[0092] According to an embodiment of the present invention, test rig 14 can be modified for carrying out testing of asphaltene or other scale-forming inhibitors. Inhibitor testing is performed to check the effectiveness of the chemicals in preventing the scaling of asphaltene or other scale-forming particles. Also, various coated pipelines are available which restricts the deposition of asphaltene or other scale-forming particles. The test simulation apparatus 100 can be used to test the effectiveness of these coating economically by coating the spool piece with the test coating.
[0093] Part 14 in FIG.1 and FIG.2 indicates a system comprising mainly a circulating pipeline and a high flowrate pump where deposition of asphaltene particles will be studied. The main aim of the present invention is to provide a high enough residence time inside the unique circulating loop structure pipelines for the asphaltene particles to deposit while maintaining a high flow rate i.e., turbulent flow of liquids inside the pipelines. Additionally, this same apparatus can be used to study any chemical species (examples: calcium carbonate, barium sulfate) that precipitates from a liquid and deposits on the pipe walls. When studying the deposition of other species, the fluid to be tested is placed in the test fluid tank ‘1’ and the precipitating solution is placed in the precipitant tank ‘7’. The deposit would then be studied by using appropriate chemicals, replacing toluene, to dissolve the deposit; for example, dilute or weak acid to dissolve CaCO3 scale. Subsequent analysis for Calcium is done using known analytical methods.
[0094] According to an embodiment of the present invention, the ratio of the mixture of test fluid and precipitant is generally selected based on the precipitation rate of the solid particles from test fluid mixture, wherein generally a ratio is selected from 1:0.25 to 1:40 volumetric ratio of crude oil (one of the test fluid) and precipitant (preferably n-heptane) based on the higher precipitation of asphaltene particles from crude oil and lower dilution of crude oil.
[0095] The present invention provides a method and system for solid deposition studies in tubular to achieve proper flow fields scalable to oil field conditions varying from laminar to fully turbulent.

EXAMPLE 1
[0096] A system and method to analyse asphaltene or other scale-forming deposition but using a pipeline geometry was developed to achieve the correct flow fields, turbulence levels, and residence time.
[0097] Since the current invention uses pipelines for the deposition test section and uses pumps for creating sufficient velocity to achieve turbulent flow, a high volumetric flow rate (more than 2 m3/h) was needed. The high flow rate makes it difficult to maintain a residence time of 50 minutes or more in pipelines of reasonable length (pilot scale) and keep the required amount of oil to a low volume. To achieve a turbulent flow as well as a high residence time of liquid inside the pipeline, it is thought to create a process that comprises a circulation pipeline with a high flow rate pump inserted into it. A continuous injection and discharge to the unique circulating loop structure (named as Test Rig here) are maintained using other low flow rate pumps. This approach can simultaneously achieve turbulent flow of liquids inside the test rig thereby generating a correct flow field as well as achieve the necessary residence time of liquids inside the process by using a lower injection rate (varied from 1 to 120 ml/min) into the circulating flow.
[0098] The method used to precipitate the solids such as asphaltenes in this invention is the same as other researchers who use precipitant like n-alkanes (pentane, hexane, heptane) to change the test fluid or crude oil composition and induce solid precipitation. The injection method in this invention allows adjusting the relative ratios of injected test fluid and precipitant. It also allows adjusting the position of the injection such that the test fluid can be injected upstream or downstream of the injected precipitant. This may be important in the experimental design since the solid particle morphology is likely one of the controlling parameters in deposition rate.

EXAMPLE 2
[0099] Crude oil or test fluid to be studied is stored at tank 1 and the temperature is monitored by using a temperature transmitter 2 while the test fluid is connected to a low flow rate and high discharge pressure pump 6 and flow is controlled using a flow controlling unit 3. A shut-off valve 5 is placed on the pipelines connecting to the pump 6 suction. A flow meter 4 is placed on the upstream side of pump 6 on pipeline P1. The discharge of pump 6 is connected to the Test Rig 14 (unique circulating loop structure) at connection point 12 and a non-return valve 11 is placed on the upstream side of injection point 12. The precipitant (ex. n-heptane) is stored inside tank 7 and connected to the suction of a low flow rate and high discharge pressure pump 10. A shut-off valve 17 is placed on the pipelines connecting to the suction of pump 10 and a flow controlling unit 8 is attached to the pump. Flow meter 9 is placed on the upstream side of pump 10 on the P2 pipeline. The discharge of pump 10 is connected to the Test Rig 14 at connection point 13 and a non-return valve 35 is placed on the upstream side of injection point 13. Both connection points 12 and 13 are placed on the Test Rig 14 in close proximity. The withdrawal of liquid takes place at the Test Rig connection point 15. A pipeline P7 is connected from point 15 to the waste drum 19 via a line with a shut-off valve 16 and a pressure regulator 18.
[00100] Test Rig 14 is a closed loop in a horizontal plane as described in FIG. 2 where it has two inlet streams at connecting points 12 & 13 previously described in FIG. 1. The inlet stream connection 12 is the oil inlet and inlet stream 13 is the precipitant inlet. Pipelines P3, P4, P5, P6 are used to create a closed flow loop with 3-diameter (or greater) curvature elbows (21, 24, 31, 34) at the bending points of pipelines. Thus, each pipeline creates a limb of the closed flow loop in a rectangular manner. Each limb of the Test Rig is connected to temperature transmitters 22, 29, 32, 41 and pressure transmitters 23, 30, 39, 40. A high flow rate pump 26 capable of withstanding high pressure is controlled by flow controlling unit 33. Pump 26 and control unit 33 are placed at the P6 limb of the apparatus which is followed by a non-return valve 27 at the discharge of the pump. A mass flow meter 28 is connected after Non-Return Valve 27. A spool piece 38 is placed on limb P4 at approximately 3 diameters downstream of elbow 34 with inlets 12 and 13 placed 5 diameters upstream of elbow 34. This placement is to improve mixing at the mixing point and through the elbow while also having a short residence time to prevent the nascent asphaltene or other scale-forming particles from agglomerating instead of depositing on the walls of the spool piece 38. Pipeline P8 is connected horizontally to the limb P4 at the downstream side of the spool piece 38. A pressure safety valve 36 is placed on pipeline P8. Pipeline P9 is oriented in a vertical direction and placed downstream of pipeline P8. The top portion of pipeline P9 acts as a vent port having a shut-off valve 37 while the bottom portion of P9 acts as a drain port having a shut-off valve 20. Test Rig 14 has an outlet port 15 at limb P7 which drains the mixture into the waste drum 19 as shown in FIG. 1.

[00101] Function and purpose of each part: Tanks 1 and 7 are used to store oil and precipitant, respectively, for injecting into Test Rig 14. Pump 6 is connected using pipeline P1 to inject the test fluid at point 12 and the liquid flow rate is controlled by a controlling unit 3 attached to pump 6. The flow rate of test fluid in pipeline P1 is measured by a liquid flow meter 4. Similarly, pump 10 is used to inject precipitant into the Test Rig at point 13 and this pump is accompanied by a flow controlling unit 8 that is used to control the injection rate. Pipeline P2 is used to transport the precipitant into Test Rig 14 while it has a flow meter 9 to measure the injection rate of n-alkane. Non-return valves 11, and 35 are placed on the pipelines P1, and P2 before injection points 12, and 13 respectively, to prevent the backward flow of mixture.
[00102] The Test Rig 14 has a high flow rate pump 26 for pumping the liquids in the circulation loop such that turbulent flow can be achieved. The flow rate is controlled using a flow controlling device 33 connected to the pump and the mass flow meter 28 is used to measure the mass flow rate of the mixture of test fluid and n-heptane inside the circulation loop 14. A non-return valve 27 is placed at the discharge of pump 26 to prevent the backward flow of liquid into the pump. Measurement of other parameters like temperature and pressure are done using temperature transmitters and pressure transducers connected to each limb of the Test Rig 14. Spool piece 38 can be removed to measure the amount of asphaltene or scale deposited on the inside of the pipe after completion of the experiment and also to observe any aging, compaction, or consolidation of the deposit. A pressure safety valve 36 is provided at pipeline P8 to prevent any mishap. A drainage port with a shut-off valve 20 is provided to drain the mixture from Test Rig 14 after completion of the experiment and a vent port with a shut-off valve 37 is placed on the pipeline P9 for venting all air/gas during the initial filling of the Test Rig. Connection point 15 is where the mixture of oil and precipitant is drawn out of Test Rig 14 using a pipeline P7. A shut-off valve 16 and a pressure regulator 18 are placed on pipeline P7 to withdraw mixture at connection point 15 while maintaining constant pressure inside the Test Rig 14.

[00103] Operation of the present invention: Initially, Test Rig 14 is filled by injecting both test fluid and precipitant into it. A constant composition of test fluid and precipitant is maintained throughout experiments. The composition or ratio of the mixture is decided based on experimental design and the need to have a large amount of precipitated solid particles. Generally, a 1:40 volumetric ratio of crude oil and n-alkane (preferably n-heptane) is used in asphaltene deposition experiments because it provides what is considered complete precipitation of asphaltenes from crude oil.
[00104] After filling Test Rig 14 with the two components i.e. test fluid and precipitant, continuous injection of both components is carried out at points 12 and 13 using a low flow rate and high discharge pressure pump 6 & 10. At the same time, a total flow rate (sum of the flow rate of test fluid and precipitant) that is injected is withdrawn at point 15 for maintaining a constant amount of the mixture inside the loop. A high flow rate pump 26 is turned on to circulate the fluids, create the desired turbulence, and ensure proper mixing of test fluid and precipitant occurs. This leads to the precipitation of asphaltene particles when the test fluid is crude oil and precipitation of BaSO4 when the test fluid is formation water which is followed by the deposition of solid particles on the inner surface of the pipelines in the Test Rig. Test parameters like temperature, pressure at various locations, and flow rates of different streams like test fluid, precipitant, and mixture are recorded during the experiments.
[00105] Variations and modifications of the Test Rig 14 (not specifically diagrammed herein) can include additional ports for testing asphaltene or other scale-forming inhibitors, or coatings on the spool piece purported to reduce deposition of scale-forming solids.
[00106] At least two injection pumps 6 & 10 having a lower flow rate and higher discharge pressure such as syringe pumps or HPLC pumps are selected for the operation. Pump 26 which is a higher flow rate pump and capable of handling higher pressure both at the suction and discharge side is selected.
[00107] Test Rig 14 is made using large enough pipe sizes (1 inch or more) to achieve turbulent flow and making it a closed chamber with an oil injection point 12 and a precipitant injection point 13 and one discharge point 15.
[00108] According to an embodiment, with no modifications, this same apparatus can be used to test scale inhibitors for oilfield brines. Oilfield brines will often form Calcium Carbonate, Calcium Sulfate, or Barium Sulfate precipitates and deposits. These form because of changes in temperature, pressure, and/or mixing of waters. When they deposit, they are referred to as scale formation inside the piping. Scale inhibitors can be tested in this apparatus by loading up the two tanks with various brines that will form the precipitate when mixed. The inhibitor can be in one of the two brines or injected through a third port on the Test Rig.
[00109] According to an embodiment of the present invention, the method for analysis of asphaltene or any other solid deposition in pipelines comprises filling the tank assembly 1 with test fluid and tank assembly 7 with a precipitant, injecting a test fluid in connecting pipeline ‘P1’ through a low flow rate & high discharge pressure pump 6, injecting the precipitant in connecting pipeline ‘P2’ through low flow rate & high discharge pressure pump 10, filling a test rig 14 with continuous injection of the test fluid and the precipitant through connections ports 12 and 13, maintaining a desired temperature of the bulk mixture inside the Test rig 14 using external heat tracers to the pipelines (P3, P4, P5, P6), setting a desired pressure at which the deposition studies need to be carried out in Test Rig 14 using a pressure regulator 18 placed in the pipeline P7, injecting the test fluid and precipitant into the circulating test rig 14 through inlet streams 12 and 13. As the injection continues, the excess liquid mixture will go to the waste drum 19 to maintain constant pressure inside Test Rig 14. Turn on pump 26 and maintain a desired circulation flow rate in Test Rig 14 based on the flow regime (laminar, transition, and turbulent) and Reynolds number where deposition studies need to be carried out. Carry out deposition test for a particular time duration (like 24h, 72h) and during test, all data of temperature, pressure, and flow rates are recorded. After completion of the deposition test, the liquid mixture is drained out using drainage port 20, and solids deposition from test fluid & precipitant mixture are collected by solvent washing. Actual asphaltene content is determined by evaporating solvent, collecting the residue, and doing its analytical analysis.

G) ADVANTAGES OF INVENTION
[00110] The present invention provides a system and method for evaluating asphaltene or other scale-forming deposition. The test apparatus maintains a high flow rate or a turbulent flow of liquids inside the pipelines at a low injection rate. The test apparatus of the present invention provides high residence time of liquids inside the pipelines for the asphaltene or other solid particles to deposit. The test apparatus of the present invention has pipelines with larger diameter (greater than 1 inch) to simulate real flow behaviour of liquids inside pipelines. The apparatus of the present invention is simple, efficient and economical to make.
[00111] The present invention also provides an improved method for evaluating asphaltene or other scale-forming deposition in pipelines and likewise. The operational cost for carrying out analysis of asphaltene or other scale-forming deposition in pipelines using the method of present invention is highly economical.
[00112] The present invention relates to the asphaltene deposition apparatus which can be used mostly by the upstream, midstream, downstream oil and gas industry and to carry out deposition tests similar to the field conditions and develop a model which fits the experimental data. This apparatus and process design is concerned with asphaltene deposition studies under various flow regimes while using precipitant (n-alkane) such as n-heptane, n-pentane, and n-propane to produce asphaltene particles and observe their depositional behaviour. The key ability is to achieve turbulent pipe flow such that the velocity and shear fields are correct, unlike other test geometries currently in use.
[00113] The present invention allows for the full range of pipe flow regimes (laminar, transition, turbulent) to be maintained during the deposition experiments. Furthermore, the geometry is a pipe geometry which gives the correct flow and shear fields, unlike the shear deposition cell.
[00114] The present invention can accommodate experiments at high pressure which allows live oil samples to be tested.
[00115] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the claims presented in the complete specification or non-provisional application.
,CLAIMS:Claims:
We Claim:
1. A system 100 for analysis of asphaltene or other scale-forming deposition in pipelines, comprises:
a pair of tank assembly, wherein one tank assembly is a test fluid tank assembly 1 and another tank assembly is precipitant tank assembly 7;
at least two low flow rate pumps 6 and 10;
a plurality of flow controlling units 3 and 8;
at least two flow meters 4 and 9;
at least two inlet streams 12 and 13;
a plurality of connecting pipelines ‘P1’, ‘P2’ and ‘P7’;
a plurality of shut off valves 5, 17, and 16;
a plurality of check valves 11, and 35;
a pressure regulator 18;
a circulating Test Rig 14; and
a waste drum 19.
2. The system 100 as claimed in claim 1, wherein a temperature transmitter 2 is attached to the test fluid tank assembly 1.
3. The system 100 as claimed in claim 1, wherein the connecting pipeline ‘P1’ is present between test fluid tank assembly 1 and circulating Test Rig 14, wherein the connecting pipeline ‘P2’ is present between is precipitant tank assembly 7 and circulating test rig 14, wherein the connecting pipeline ‘P7’ is present between the circulating test rig 14 and the waste drum 19.
4. The system 100 as claimed in claim 1, wherein the inlet stream 12 is present between the test fluid tank assembly 1 and circulating Test Rig 14.
5. The system 100 as claimed in claim 1, wherein the inlet stream 13 is present between the precipitant tank assembly 7 and circulating Test Rig 14.
6. The system 100 as claimed in claim 1, wherein the diameter of the connecting pipelines ‘P1’, ‘P2’ and ‘P7’ is less than 1 inch.
7. The system 100 as claimed in claim 1, wherein the circulating test rig 14 forms a ‘4-limbed’ shaped closed test rig system with 3-diameter (or greater) curvature elbows 21, 24, 31, 34 at the bending points with the length of one or more of the limbs being greater than 10 diameters.
8. The system 100 as claimed in claim 1, wherein the circulating Test Rig 14 further comprises:
a high flow rate pump 26;
a non-return valve 27;
a mass flow meter 28;
a flow controlling unit 33;
at least four connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6’;
at least four bending points 21, 24, 31, 34;
a plurality of temperature transmitters 22, 29 32, and 41;
a plurality of pressure transducers 23, 30, 39, and 40;
a spool piece 38;
a discharge point 15;
at least two pipelines ‘P8’, ‘P9’
a pressure safety valve (psv) 36;
a vent port 37; and
a drainage port 20.
9. The circulating Test Rig 14 as claimed in claim 8, wherein the high flow rate pump 26 and the flow controlling unit 33 is present on the connecting pipeline ‘P6’.
10. The circulating test rig 14 as claimed in claim 8, wherein the non-return valve 27 is present at the discharge of the high flow rate pump 26.
11. The circulating test rig 14 as claimed in claim 8, wherein the mass flow meter 28 is present succeeding to the non-return valve 27 on the connecting pipeline ‘P6’.
12. The circulating test rig 14 as claimed in claim 8, wherein the discharge point 15 is present on the connecting pipeline ‘P5’.
13. The circulating test rig 14 as claimed in claim 8, wherein the spool piece 38 is present on the connecting pipeline ‘P4’.
14. The circulating test rig 14 as claimed in claim 8, wherein the flow is unidirectional flow.
15. The circulating test rig 14 as claimed in claim 8, wherein the diameter of the connecting pipelines ‘P3’, ‘P4’, ‘P5’ and ‘P6’ is greater than or equal to 1 inch.
16. The system 100 as claimed in claim 1, wherein the system maintains a higher residence time up to 50 minutes or greater than that inside the pipelines while achieving a higher shear stress on the walls of pipeline.
17. A method for analysis of asphaltene or other scale-forming deposition in pipelines comprises:
(k) filling a tank assembly 1 with a test fluid and a tank assembly 7 with a precipitant solution;
(l) injecting a test fluid in a connecting pipeline ‘P1’ through a low flow rate & high discharge pressure pump 6;
(m) injecting the precipitant solution in a connecting pipeline ‘P2’ through a low flow rate & high discharge pressure pump 10;
(n) filling a test rig 14 with a continuous injection of the test fluid and the precipitant through connections ports 12 and 13;
(o) maintaining a desired temperature inside the Test rig 14 using external heat tracers to the pipelines P3, P4, P5, P6;
(p) setting a desired pressure at which a deposition studies need to be carried out in Test Rig 14 using a pressure regulator 18 placed in the pipeline P7;
(q) turning on a pump 26 and maintaining a desired circulation flow rate in Test Rig 14;
(r) carrying out deposition test for a particular time duration and recording all the desired parameters;
(s) draining out the liquid mixture after completion of the deposition test using drainage port 20, and collecting solids deposition from test fluid & precipitant mixture by solvent washing; and
(t) determining the actual solid content.
18. The method as claimed in claim 17, wherein the precipitant is n-alkane for crude oil as test fluid.
19. The method as claimed in claim 17, wherein the method is used for determining chemical species such as calcium carbonate, barium sulfate that precipitates from a liquid and deposits on the pipe walls.