Field of the Invention
[0001] The present invention generally relates to the field of hydrocarbon exploration, and more particularly to a method for assessing shale gas potential of unconventional reservoir wells based on an estimation of Total Organic Carbon (TOC) throughout a selected depth range of the reservoir well from conventionally recorded log data associated with said reservoir wells.
Background of the Invention
[0002] The estimation of potential of a reservoir is an essential step in hydrocarbon exploration. One of the key elements which can be used for assessing the presence of hydrocarbon (preferably shale gas) potential of a reservoir well is Total Organic Carbon (TOC) associated with a formation of the reservoir well. Therefore, it is essential to estimate TOC accurately for accurate assessment of shale gas potential of the reservoir well.
[0003] One of the existing methods for estimation of TOC logs rely on analysis of formation samples also known as core samples retrieved from a depth of the reservoir well. However, it has been observed that analysis of a core sample in a laboratory provides point value of TOC at the specific depth of the reservoir well and does not reflect TOC value throughout entire depth of the reservoir well, thereby providing inaccuracies in the continuous TOC log. Another method which is often relied upon for generating a continuous TOC log is "Passey's method". Passey's method employs conventionally recorded sonic and resistivity log data for estimating TOC log. However, Passey's method is highly dependent on appropriate selection of shale baseline and also requires correct estimation of Level of Organic Maturity (LOM) of the formation of the reservoir well, which is usually determined from geochemical measurements. Moreover, it has been observed that the deep resistivity and sonic logs employed for baseline selection in non-organic shale in Passey's method provides inaccurate results in low porosity sections as well as in uncompacted sections. Further, the TOC background levels are known to vary

regionally, as a result the Passey's method may lead to underestimating the TOC value in over mature source rocks, thereby leading to inaccuracies in assessment of the reservoir well.
[0004] In addition to the above methods, TOC can be estimated indirectly based on a combination of conventionally recorded density log with advanced logs such as Combinable Magnetic Resonance (CMR), and ECS. Alternatively TOC can also be read directly from Litho-scanner data. However, generation of the CMR and ECS logs involve the use of expensive equipment, thereby leading to higher costs, and further limiting routine recording of logs for every reservoir well in the oil field.
[0005] In light of the aforementioned drawbacks, there is a need for a method which can assess shale gas potential of unconventional reservoir wells based on an estimation of continuous Total Organic Carbon (TOC) i.e. TOC throughout a selected depth range of the well. There is a need for a method which provides a continuous TOC log with improved accuracy. There is a need for a method which can assess shale gas potential of new as well as old reservoir wells. Further, there is a need for a method which is based on conventionally recorded logs which are readily available for each of the reservoir wells. Furthermore, there is a need for a method which has wider applicability and is easy to implement. Yet further, there is a need for a method which is economical.
Summary of the invention
[0006] In various embodiments of the present invention a method for assessing shale gas potential of an unconventional formation in a reservoir well is provided. The method comprises identifying one or more types of clay and minerals associated with the unconventional formation in the reservoir well. The method further comprises evaluating continuous effective porosity, continuous effective hydrocarbon saturation, and continuous volume of the identified one or more types of clay and minerals throughout a selected depth range of the unconventional formation based on conventionally recorded continuous logs associated with the unconventional formation. Further, the method comprises evaluating continuous

density porosity throughout the selected depth range of the unconventional formation based on a conventionally recorded continuous density log. Furthermore, the method comprises evaluating continuous volume of kerogen throughout the selected depth range of the unconventional formation based on the evaluated continuous effective porosity, the continuous density porosity, and a continuous combined volume of the identified one or more types of clay. Yet further, the method comprises evaluating continuous volume of organic rich shale throughout the selected depth range of the unconventional formation using conventionally recorded continuous Gamma Ray (GR) log and continuous deep Resistivity log associated with the unconventional formation. Yet further, the method comprises generating a continuous Total Organic Carbon (TOC) log for the selected depth range of the unconventional formation based on the continuous volume of organic rich shale and continuous volume of kerogen. Finally, the method comprises assessing shale gas potential of the selected depth range of the unconventional formation based on the generated continuous TOC log, where a high value of TOC in the selected depth range is indicative of high shale gas potential. The method of the present invention provides for estimation of TOC values of selected unconventional formation in the reservoir well using three basic logs, namely Resistivity, GR and density, thereby eliminating cost of hi-tech equipments.
Brief Description of the Drawings
[0007] The present invention is described by way of embodiments illustrated in the accompanying drawings wherein:
[0008] Figure 1 is a flowchart illustrating a method for assessing shale gas potential of an unconventional formation in a reservoir well, in accordance with various embodiments of the present invention;
[0009] Figure 2 illustrates an exemplary cross plot between core TOC and Density log associated with a selected depth range of the unconventional formation, in accordance with various embodiments of the present invention; and

[0010] Figure 3 illustrates an exemplary petro-physical representation and porosity distribution of the unconventional formation of the reservoir well, in accordance with various embodiments of the present invention; and
[0011] Figure 4 illustrates a comparison of TOC values estimated for a selected depth range of the unconventional formation in accordance with various embodiments of the present invention with TOC values obtained from core, and Litho-Scanner log data.
Detailed Description of the Invention
[0012] The disclosure is provided in order to enable a person having ordinary skill in the art to practice the invention. Exemplary embodiments herein are provided only for illustrative purposes and various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. The terminology and phraseology used herein is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed herein. For purposes of clarity, details relating to technical material that is known in the technical fields related to the invention have been briefly described or omitted so as not to unnecessarily obscure the present invention. It is to be noted that, as used in the specification by the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those skilled in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. The term "continuous log" as used in the specification refers to detailed logs that record sample values of predefined formation parameters throughout the selected depth range of the reservoir well with a selected sampling rate. The term "continuous" before density porosity, effective

porosity, effective hydrocarbon saturation, TOC, volume of kerogen and volume of organic rich shale as used in the specification is indicative that said parameters are calculated throughout the entire selected depth range of the formation.
[0013] The present invention discloses a method for assessing hydrocarbon potential of unconventional reservoir wells. In particular, the present invention discloses a method for assessing shale gas potential of unconventional reservoir wells based on an estimation of continuous Total Organic Carbon (TOC) log for a selected depth range of the reservoir well using conventionally recorded continuous log data of said reservoir wells. In operation, the method of the present invention provides for identifying one or more types of clay and minerals in a selected unconventional formation of the reservoir well using Natural Gamma Ray Spectroscopy (NGS) cross-plot analysis and sedimentological core studies. Further, the present invention provides for evaluating formation parameters including effective porosity, effective hydrocarbon saturation, and volume of the identified one or more type of clay and minerals throughout the depth of unconventional formation based on the conventionally recorded logs using petro physical analysis. The conventionally recorded logs include at least Gamma ray, resistivity, density, neutron log and optionally sonic. The present invention further provides for evaluating continuous density porosity associated with the selected depth range of unconventional formation in the reservoir well based on conventionally recorded density log of the unconventional formation, inorganic grain density of the unconventional formation matrix and density of fluid in the unconventional formation. Further, continuous volume of kerogen associated with the selected depth range of the unconventional formation is evaluated based on the effective porosity, the density porosity and the volume of the identified one or more type of clay. Yet further, volume of organic rich shale associated with the selected depth range of the unconventional formation of the reservoir well is evaluated using conventionally recorded continuous Gamma ray log and deep Resistivity log of the reservoir well. Yet further, the present invention provides for evaluating continuous Total Organic Carbon (TOC) associated with the selected depth range of the

unconventional formation of the reservoir well based on the volume of organic shale and volume of kerogen, where TOC is the product of volume of organic shale and volume of kerogen. Finally, the present invention provides for assessing the shale gas potential of the reservoir well based on the TOC evaluated for the selected depth range of the unconventional formation, where higher TOC is indicative of high shale gas potential.
[0014] The present invention would now be discussed in context of embodiments as illustrated in the accompanying drawings.
[0015] Referring to Figure 1, a flowchart illustrating a method for assessing shale gas potential of an unconventional formation in a reservoir well, in accordance with various embodiments of the present invention.
[0016] At step 102, one or more types of clay and minerals associated with a selected unconventional formation of the reservoir well are identified. In an embodiment of the present invention, the one or more types of clay and minerals are identified using Natural Gamma Ray Spectroscopy (NGS) cross-plot analysis and validated using sedimentological core studies. In operation, NGS cross-plots also referred to as Thorium Vs Potassium curves cross-plot are generated to determine the clay and heavy mineral composition of the selected unconventional formation. Further, sedimentological studies are performed, where the core samples from a specific depth within the selected unconventional formation of the reservoir well are examined megascopically for lithology description and studied microscopically for petrographic analysis to understand the mineralogy and texture. Furthermore, clay and minerals in the selected unconventional formation are identified by carrying out X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis on core/cutting samples of the selected unconventional formation.
[0017] In accordance with an embodiment of the present invention, the one or more types of clay and minerals in the selected unconventional formation determined through NGS cross-plots are validated against the results of sedimentological core

studies of the core samples from unconventional formation of the same reservoir well. In an example, the reservoir well may be considered to have a depth ranging from 1000m-4000m. Further, the unconventional formation may have depth ranging from 3000-4000m. In the aforementioned example, the one or more types of clay and minerals in the unconventional formation ranging from 3000-4000m are identified using NGS cross-plot analysis. Further, the core samples from the unconventional formation ranging from 3000-4000m are extracted for sedimentological studies to validate the one or more types of clay and minerals in the unconventional formation identified using NGS cross-plot analysis. In an exemplary embodiment of the present invention, the core samples may be extracted from a point depth for example 3000m, 3010m etc. In another exemplary embodiments of the present invention, the core samples may be extracted from a selected depth range of 3000-4000m at predetermined intervals, for instance 3000-3005m, 3005-3010m etc.
[0018] At step 104, formation parameters including continuous effective porosity, continuous effective hydrocarbon saturation, and continuous volume of the identified one or more types of clay and minerals associated with the selected depth range of the unconventional formation are evaluated based on conventionally recorded continuous logs using petro physical analysis. In accordance with various embodiments of the present invention, the conventionally recorded continuous logs include Gamma ray, resistivity, density, neutron log and sonic. In a preferred embodiment of the present invention, the conventionally recorded continuous logs include Gamma ray, resistivity, density and neutron log. It is to be understood that the conventionally recorded logs may be recorded throughout the depth of the reservoir well via a well logging tool and stored in a database. In accordance with an embodiment of the present invention, petro physical analysis includes building of a multi-mineral log processing model associated with the selected unconventional formation. In an embodiment of the present invention, the multi-mineral log processing model is built by incorporating the identified one or more types of clay and minerals with conventionally recorded continuous logs associated

with the reservoir well via a computing device. In an embodiment of the present invention, based on the identified one or more types of clay and minerals, and values of input parameters including Gamma ray, resistivity, density and neutron, theoretical logs responses are calculated and compared with the actual conventionally recorded logs(Gamma ray, resistivity, density and neutron) until a satisfactory multi-mineral log processing model is achieved. In an exemplary embodiment of the present invention, the values of input parameters are presumed or preselected based on the identified one or more types of clay and minerals. Further, the values of formation parameters including effective porosity, effective hydrocarbon saturation, and volume of the identified one or more types of clay and minerals throughout the selected depth range of unconventional formation are evaluated based on the multi-mineral log processing model.
[0019] At step 106, evaluating density porosity i.e. the density porosity throughout the selected depth range of the unconventional formation of the reservoir well is evaluated based on conventionally recorded continuous density log, inorganic grain density of the unconventional formation matrix and density of fluid in the unconventional formation. In an embodiment of the present invention, the continuous density porosity of the unconventional formation is evaluated by incorporating density values from conventionally recorded continuous density log, the inorganic grain density of the unconventional formation matrix and the density of fluid in the unconventional formation in the equation reproduced below:
[0020] DEN_POR = (pma-pb)/(pma-pfl); where pma is the Inorganic grain density of unconventional formation matrix; pfl is the Density of the fluid at point depth; and pb- is continuous density log (i.e. -density values throughout the depth of the unconventional formation).
[0021] In operation, in an embodiment of the present invention, the Core TOC values of core/cutting samples obtained from a particular depth of the selected unconventional formation are determined. In particular, the core TOC values are determined in the geochemical laboratories using pyrolysis techniques in which the

obtained core samples are heated at different temperatures to release organic compounds. Further, the total amount of carbon in organic compound released from the given sample is measured, which gives TOC value at the particular depth from where the core sample was extracted. For example, if the core sample is extracted from a depth of 3000m from the selected unconventional formation, then the core determined TOC value is representative of Total Organic Carbon at depth 3000m.
[0022] Further, the Inorganic grain density(pma) of the unconventional formation matrix is determined based on a cross plot between the determined core TOC values and the conventionally recorded density log. As exemplified in FIG. 2, the value of density at zero TOC is obtained by extrapolation of the least square fit line, and the value of inorganic grain density obtained from the cross-plot is determined to be 2.80 gm/c3. In an exemplary embodiment of the present invention, the inorganic grain density (obtained from cross-plot) is validated by core inorganic grain density obtained through petrophysical studies of core sample from the unconventional formation. In an experiment, the inorganic grain density obtained through petrophysical studies was around 2.795gm/c3, which is substantially close to 2.80 gm/c3 as obtained from the cross-plot.
[0023] In an embodiment of the present invention, the Density of the fluid (pfl) is obtained from the production data of the unconventional formation. The production data may be obtained for the same unconventional formation either from the reservoir well being studied or from a nearby reservoir well of the same field. In a preferred embodiment of the present invention, pfl is density of hydrocarbon produced in the unconventional formation.
[0024] Further, the determined inorganic grain density of the unconventional formation matrix and the density of fluid in the unconventional formation along with the density values for the selected depth range of the unconventional formation from conventionally recorded continuous density log are incorporated in the equation: DENPOR = (pma-pb)/(pma-pfl) to compute continuous density porosity i.e. density porosity throughout a selected depth range of the unconventional

formation. In accordance with various embodiments of the present invention, the evaluated continuous density porosity provides a measure of volume of kerogen, volume of clay bound water and effective porosity throughout the selected depth range of the unconventional formation of the reservoir well.
[0025] At step 108, continuous volume of kerogen i.e. the volume of kerogen throughout the selected depth range of unconventional formation is evaluated based on the evaluated continuous effective porosity, continuous density porosity, and the continuous combined volume of the identified one or more type of clay. In operation, in accordance with various embodiments of the present invention, a combined volume of kerogen and clay bound water (VKerCBW) throughout the depth of unconventional formation is evaluated based on the continuous effective porosity and continuous density porosity. In an embodiment of the present invention, the combined volume of kerogen and clay bound water in the unconventional formation is evaluated based on a difference between density porosity as evaluated at step 106 and effective porosity as evaluated at step 104. Further, the continuous volume of kerogen in the unconventional formation is evaluated by eliminating the volume of clay bound water from the combined volume of kerogen and clay bound water (VKerCBW). In an embodiment of the present invention, the volume of clay bound water from the combined volume of kerogen and clay bound water (VKerCBW) is eliminated by introducing a coefficient (3. In an embodiment of the present invention, the coefficient (3 is representative of the volume of clay bound water. In an exemplary embodiment of the present invention, the value of coefficient (3 is determined based on the combined volume of the identified one or more type of clay estimated at step 104 using experimental analysis.
[0026] In an experiment, where the identified one or more types of clay throughout a selected depth range of the unconventional formation were illite, kalonite and chlorite, the fraction volume of combined clay (indicated as clay mineral in Figure 3) at a depth was observed to be ranging from 0.7 to 0.8, as a result an average volume of clay was selected as 0.75. Further, it was assumed that the combined

volume of the identified one or more type of clay at the same depth of the unconventional formation includes 10 % of clay bound water. Therefore, value of clay bound water ((3) was calculated as 10 % of 0.75, which is 0.075. Finally, the volume of kerogen at the same depth of unconventional formation was evaluated as a product of combined volume of kerogen and clay bound water and (3 as reproduced below.
[0027] VKerC at depth A of the unconventional formation = VKerCBW at depth A of the unconventional formation * (3;
[0028] where VKerC = Volume of kerogen, VKerCBW = combined volume of kerogen and clay bound water, (3 = volume of clay bound water.
[0029] In an example, where the selected unconventional formation has a depth of 3000-4000m, the volume of kerogen at each depth from 3000-4000m with a preselected sampling rate is evaluated. In accordance with various embodiments of the present invention, a continuous volume of kerogen curve is obtained from the values of volume of kerogen throughout the depth of the unconventional formation.
[0030] The volume of kerogen evaluated in accordance with the present invention were validated via an experiment. In the experiment the volume of kerogen evaluated in accordance with the present invention was compared with the volume of kerogen obtained from AlogR method (Passey's method). As shown in Figure 4, it was observed that the volume of kerogen (VKERC) curve obtained in accordance with step 108 of the present invention shown by dashed line matched with the volume of kerogen (VOLKEROGENDLR) in black solid line obtained from AlogR method.
[0031] It is to be understood that the volume of Kerogen in the unconventional formation is representative of the presence of organic content in the formation. The present invention emphasises on petro physical evaluation of the reservoir wells which is essential for assessing shale gas potential. It is to be noted that shale gas in the reservoir well is present in adsorbed gas in the organic matter and "free gas"

trapped in the pores of kerogen and also in the inorganic portion of formation matrix. Further, the shale gas may also be present in open natural fractures if such fractures are present. Therefore, the volume of kerogen is vital as free gas occupies pores of kerogen, and effective porosity is vital as it considers the effect of different clay minerals, heavy minerals and conductive minerals such as pyrite etc.
[0032] At step 110, continuous volume of organic rich shale i.e. volume of organic rich shale throughout the selected depth range of the unconventional formation of the reservoir well is evaluated using conventionally recorded continuous Gamma Ray (GR) log and continuous deep Resistivity log associated with the reservoir well. In an embodiment of the present invention, the continuous volume of shale bearing brine content associated with the selected depth range of the unconventional formation (for e.g.:-3000-4000m) is determined from the resistivity log. Further, the continuous volume of shale bearing both brine and organic matter associated with the selected depth range of the unconventional formation (for e.g.:-3000-4000m) is determined from GR log. In an embodiment of the present invention, the volume of organic rich shale throughout the depth of unconventional formation (for e.g.:-3000-4000m) is calculated by subtracting volume of shale bearing brine content from volume of shale bearing both brine and organic matter. It is to be understood that the depth 3000-4000m is only for the purposes of understanding. The actual depth of the unconventional formation may vary depending on the oil field.
[0033] At step 112, Total Organic Carbon (TOC) log for the selected depth range of the unconventional formation of the reservoir well is generated based on the continuous volume of organic rich shale and continuous volume of kerogen. In an embodiment of the present invention, continuous TOC values throughout the selected depth range of the unconventional formation are evaluated as a product of the volume of organic rich shale and the volume of kerogen at each depth within the selected depth range. In particular, the Total Organic Carbon (TOC) at a depth of the unconventional formation is determined as a product of volume of organic shale and volume of kerogen at the same depth.

[0034] TOC of at depth A of the unconventional formation = Volume of organic shale at depth A* Volume of kerogen at depth A.
[0035] In an example, where the selected unconventional formation has a depth of 3000-4000m, the TOC value at each depth from 3000-4000m with a preselected sampling rate is evaluated manually or computing device. In accordance with various embodiments of the present invention, a continuous TOC log is generated based on the TOC values throughout the depth of the unconventional formation.
[0036] At step 114, the shale gas potential of the selected unconventional formation in the reservoir well is assessed based on the generated continuous TOC log. In accordance with various embodiments of the present invention, high value of TOC is indicative of high shale gas potential of the unconventional formation. Further, low value of TOC is indicative of low shale gas potential of the unconventional formation. In an exemplary embodiment of the present invention, TOC percentage less than 1% is considered low and TOC percentage greater than 1% is considered fair.
[0037] An experiment was performed to compare the TOC values for a selected depth range of the unconventional formation obtained in accordance with the various embodiments of the present invention with TOC values derived from core sample analysis, and TOC obtained from available Litho-scanner data (hi-tech log) for the same depth of the unconventional formation. As shown in Figure 4, it was observed that the TOC values estimated for a selected depth range (3660-3800) of unconventional formation in accordance with various embodiments matches with TOC values from core samples and TOC from Litho-scanner data.
[0038] Advantageously, the method of the present invention facilitates assessment of new as well as old unconventional formations based on conventionally recorded continuous logs along with core determined relationships. The estimation of TOC by integrating results of core and log data in the present invention provides more accuracy and matches well with the actual TOC data. Further, the method of the present invention provides for estimation of TOC values of selected reservoir wells

using three basic logs, viz Resistivity, GR and density, thereby eliminating cost of hi-tech equipments.
[0039] It is to be understood that the method steps of the present invention may be carried out manually using a computing device, or may be implemented via a computing device comprising at least one processor specifically programmed to execute instructions stored in the memory for executing the method in accordance with various embodiments of the present invention.
[0040] While the exemplary embodiments of the present invention are described and illustrated herein, it will be appreciated that they are merely illustrative. It will be understood by those skilled in the art that various modifications in form and detail may be made therein without departing from the scope of the invention except as it may be described by the following claims.

We Claim:
1. A method for assessing shale gas potential of an unconventional formation in a reservoir well, said method comprising:
identifying one or more types of clay and minerals associated with the unconventional formation in the reservoir well;
evaluating continuous effective porosity, continuous effective hydrocarbon saturation, and continuous volume of the identified one or more types of clay and minerals throughout a selected depth range of the unconventional formation based on conventionally recorded continuous logs associated with the unconventional formation;
evaluating continuous density porosity throughout the selected depth range of the unconventional formation based on a conventionally recorded continuous density log;
evaluating continuous volume of kerogen throughout the selected depth range of the unconventional formation based on the evaluated continuous effective porosity, the continuous density porosity, and a continuous combined volume of the identified one or more types of clay;
evaluating continuous volume of organic rich shale throughout the selected depth range of the unconventional formation using conventionally recorded continuous Gamma Ray (GR) log and continuous deep Resistivity log associated with the unconventional formation;
generating a continuous Total Organic Carbon (TOC) log for the selected depth range of the unconventional formation based on the continuous volume of organic rich shale and continuous volume of kerogen; and
assessing shale gas potential of the selected depth range of the unconventional formation based on the generated continuous TOC log,

wherein a high value of TOC in the selected depth range is indicative of high shale gas potential.
2. The method as claimed in claim 1, wherein the one or more types of clay and minerals associated with the selected depth of the unconventional formation are identified using Natural Gamma Ray Spectroscopy (NGS) cross-plot analysis.
3. The method as claimed in claim 2, wherein the one or more types of clay and minerals identified using NGS cross-plot analysis are validated using sedimentological core studies, wherein the core samples are collected from a specific depth of the unconventional formation.
4. The method as claimed in claim 1, wherein the conventionally recorded continuous logs comprises Gamma ray, resistivity, density, and neutron log.
5. The method as claimed in claim 4, wherein the continuous effective porosity, the continuous effective hydrocarbon saturation, and the continuous volume of the identified one or more types of clay and minerals are evaluated based on the conventionally recorded continuous logs using petro physical analysis.
6. The method as claimed in claim 5, wherein the petro physical
analysis comprises building of a multi-mineral log processing model associated
with the selected unconventional formation based on the identified one or more
types of clay and minerals, and preselected values of input parameters including
Gamma ray, resistivity, density and neutron, and the conventionally recorded
continuous logs; and evaluating the continuous effective porosity, the
continuous effective hydrocarbon saturation, and the continuous volume of the
identified one or more types of clay and minerals throughout the selected depth
range of the unconventional formation based on the multi-mineral log
processing model.

7. The method as claimed in claim 1, wherein the continuous density porosity is evaluated by incorporating density values (pb) from the conventionally recorded continuous density log, an inorganic grain density(pma) of the unconventional formation matrix and a density of fluid (pfl) associated with the unconventional formation in the equation: DENPOR = (pma-pb)/(pma- pfl).
8. The method as claimed in claim 7, wherein the Inorganic grain density(pma) of the unconventional formation matrix is determined based on a cross plot between core TOC values and the density values from the conventionally recorded density log, wherein the core TOC values are calculated from core samples obtained from the selected depth range of the unconventional formation in the geochemical laboratories.
9. The method as claimed in claim 7, wherein the density of fluid (pfl) is obtained from the production data of the unconventional formation.
10.The method as claimed in claim 1, wherein the evaluation of the continuous volume of kerogen comprises:
evaluating a combined volume of kerogen and clay bound water (VKerCBW) throughout the selected depth range of the unconventional formation as a difference between continuous density porosity and continuous effective porosity; and
evaluating the continuous volume of kerogen by eliminating the volume of clay bound water ((3) from the combined volume of kerogen and clay bound water (V_Ker_CBW) throughout the selected depth range of the unconventional formation; wherein the volume of clay bound water ((3) is determined based on the combined volume of the identified one or more types of clay estimated using experimental analysis.
11. The method as claimed in claim 10, wherein the continuous volume of kerogen is evaluated as a product of combined volume of kerogen and clay

bound water, and the volume of clay bound water (R) throughout the selected depth range of the unconventional formation.
12. The method as claimed in claim 1, wherein the evaluation of continuous volume of organic rich shale comprises:
determining the continuous volume of shale bearing brine content associated with the selected depth range of the unconventional formation from the resistivity log;
determining the continuous volume of shale bearing both brine and organic matter associated with the selected depth range of the unconventional formation from GR log; and
evaluating the continuous volume of organic rich shale by subtracting the continuous volume of shale bearing brine content from volume of shale bearing both brine and organic matter.
13.The method as claimed in claim 1, wherein generating the continuous TOC log comprises evaluating TOC values continuously throughout the selected depth range of the unconventional formation as a product of the volume of organic rich shale and the volume of kerogen at each depth within the selected depth range.