Field of the Invention The present invention relates generally to the field of identification of oil and gas provinces. More particularly the present invention relates to a system and a method for identification of petroleum provinces through microgravity. Background of the Invention Seismic method is an invasive method that is used for generating an image of a subsurface of earth based on physical properties. The gravity and the magnetic methods are non-invasive geophysical methods used for measuring natural variations in gravity field and magnetic field differences between observed locations over an area of interest. Furthermore, the gravity methods have many applications in engineering and environmental studies such as locating karsts, monitoring aquifer recharge, determining geologic layer thickness and the structure of basement, estimating the mass and volume changes in geothermal reservoirs, monitoring precursors of volcanic eruptions, and monitoring gas production and carbon sequestration etc. The gravity method is also used in oil, gas, and mineral exploration. With the recent development of sensitive gravimeters, gravity survey has become one of the most used geophysical tool in applied geosciences for tasks including exploring for oil and gas fields by studying geological structures and salt dome intrusion. Conventionally, in the gravity method, gravity meters are used for identification of near sub-surface cavities inside the earth. Gravity data obtained from the gravity meter is also used for inferring basement rock lithology i.e. Si-Al or Si-Ma or granitic or basaltic or metamorphic etc. However, when the sand is thin and has limited extent, it has been observed that it is difficult to map through seismic or place development locales, particularly in deeper layers. The seismic method also suffers from environment objections and further suffers from uneven maximum depth of signal penetration due to presence of numerous volcanic structures. Further, there is a lack of clarity in subsurface imaging due to seismic energy penetration. It has also been observed that the thin reservoir layers (<20m or 30m) also create problems while measuring the seismic data. There are also logistic difficulties in the populated areas as regards to the acquisition of the seismic data. Furthermore, because of the environment permissions, time and cost are also an area of concern. [0004] In light of the aforementioned drawbacks, there is a need for a system and a method for efficient and accurate identification of hydrocarbon provinces. There is a need for a system and a method for identification of hydrocarbon provinces with high resolution gravity data through gravity surveys that is environment friendly and where large areas are covered cost effectively and in minimum time. Summary of the Invention [0005] In various embodiments of the present invention, a system for identification of petroleum provinces through microgravity is provided. The system comprises a memory for storing program instructions and a processor executing program instructions stored in the memory. The system comprises a computation engine executed by the processor and configured to receive a gravity field data and a 3-dimensional (3-D) positioning data from a point of observation of an area of interest. The computation engine is configured to compute bouguer anomaly values from the gravity field data and the 3-D positioning data. Further, the computation engine is configured to compute residual anomaly values by applying a wavelength filter on the bouguer anomaly values to identify low gravity zones, wherein the wavelength filter is applied based on parameters of the area of interest. The computation engine is further configured to compute gradient anomaly values from the bouguer anomaly values to identify high gradient zones. Finally, the computation engine is configured to identify hydrocarbon provinces based on the identified low gravity and high gradient zones. [0006] In various embodiments of the present invention, a method for identification of petroleum provinces through microgravity is provided. The method comprises receiving a gravity field data and a 3-dimensional (3-D) positioning data from a point of observation of an area of interest. The method comprises computing bouguer anomaly values from the gravity field values and the 3-D positioning values. The method further comprises computing residual anomaly values by applying a wavelength filter on the bouguer anomaly values to identify low gravity zones, wherein the wavelength filter is applied based on parameters of an area of interest. Further, the method comprises computing gradient anomaly values from the bouguer anomaly values to identify high gradient zones. Finally, the method comprises identifying hydrocarbon provinces based on the identified low gravity and high gradient zones. Brief description of the accompanying drawings [0007] The present invention is described by way of embodiments illustrated in the accompanying drawings wherein: [0008] FIG. 1 is a block diagram of a gravity meter for identification of petroleum provinces through microgravity, in accordance with an embodiment of the present invention; [0009] FIG. 2 is a detailed block diagram of a gravity data processing subsystem for identification of petroleum provinces through microgravity, in accordance with an embodiment of the present invention; [0010] FIG. 3 is a flowchart illustrating a method for identification of petroleum provinces through microgravity, in accordance with an embodiment of the present invention; [0011] FIG. 4 shows a bouguer anomaly map, in accordance with an embodiment of the present invention; [0012] FIG. 5 shows a residual anomaly map, in accordance with an embodiment of the present invention; [0013] FIG. 6 shows a gradient anomaly map, in accordance with an embodiment of the present invention; [0014] FIG. 7 shows a cross plot between residual anomaly data versus gradient anomaly data, in accordance with an embodiment of the present invention; and [0015] FIG. 8 illustrates an exemplary computer system in which various embodiments of the present invention may be implemented. Detailed description of the invention [0016] 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. [0017] The present invention would now be discussed in context of embodiments as illustrated in the accompanying drawings. [0018] FIG. 1 illustrates a block diagram of a system 100 for identification of petroleum provinces through microgravity, in accordance with an embodiment of the present invention. The system 100 comprises a gravity meter 102, a global navigation satellite system (GNSS) receiver unit 104, a communication network 106 and a gravity data processing subsystem 108. [0019] Referring to FIG. 1, the gravity meter 102 for measuring variations in earth's gravity field is shown. In an embodiment of the present invention, the gravity meter 102 is a micro level gravity meter. In an embodiment of the present invention, the gravity meter 102 is configured to measure a gravity field at a point of observation based on density differences in subsurface rocks inside the earth surface. As shown in FIG. 1, a mass 204 is suspended in the gravity meter 102 from a spring balance 202 that is used for measuring the gravity field. In the gravity meter 102, as weight of mass (mass x gravity) increases, the spring balance 202 is stretched. As the spring balance 202 stretches, an air gap capacitance changes inside the gravity meter. The change in air gap capacitance is used to measure the gravity changes. [0020] In an example, a free falling body with mass "m" near the earth surface experiences a force AF' as per the below formula F = mg = GMm/R2 where g, M and R are gravity, mass and radius of earth Or g=GM/R2 but M = density (p) x Volume (V = 4nR3/3) g = (G*4nR3/3 * p) / R2 or 4GnRp/3 Or g a p (since G, 4/3, n and R are all constants) (1) [0021] As shown in equation (1), during measurement of the gravity field data along the surface of earth at the point of observation, gravity (g) is directly proportional to density (p). Micro level variations in the gravity field provides density variations within the subsurface of earth. Therefore, from measurements of micro level variations of gravity (g) on surface of the earth from the gravity meter 102, the density variations up to 0.001 gm/cc can be inferred within sub-surface of the earth. In an exemplary embodiment of the present invention, a lower density signifies presence of hydrocarbon reserves. [0022] In an embodiment of the present invention, the gravity meter 102 measures the gravity field at a point of observation without digging or causing any damage to environment. The gravity meter 102 is configured to record gravity field data at the point of observation. In an exemplary embodiment of the present invention, the gravity meter 102 is configured to measure exact precision gravity field of the earth at the point of observation of the gravity meter 102. In an exemplary embodiment of the present invention, a plurality of gravity meters 102 may be installed at a distance of 20m-250m. In an embodiment of the present invention, the gravity field data is measured based on a depth of interest, geology of interest and a topography of interest etc. In another exemplary embodiment of the present invention, the gravity meter 102 measures the surface gravity field data for a time duration of one or two minutes at the point of observation. [0023] In an embodiment of the present invention, the GNSS receiver unit 104 is configured to generate a 3-Dimensional (3-D) positioning data of the point of observation. In an embodiment of the present invention, the 3-D positioning data corresponds to the coordinates of the point of observation. In an embodiment of the present invention, the coordinates of the point of observation are calculated using a latitude of the point of observation, longitude of the point of observation and height of the point of observation from a datum. The datum is the mathematical surface close to the surface of the earth. In an exemplary embodiment of the present invention, the mathematical surface is a reference mathematical ellipsoidal surface close to the earth's surface against which positional measurements are made for computing locations. In an example, horizontal datums are used for describing a point on the earth's surface, in latitude and longitude. In another example, vertical datums are used to measure elevations or underwater depths. In an example, in case of hills, the height of the point of observation is above the datum. In another example, in case of valleys, the height of the point of observation is below the datum. [0024] In an embodiment of the present invention, a communication network 106 is configured to transfer the gravity field data and the 3D positioning data from the gravity meter 102 and the GNSS receiver unit 104 respectively to the gravity data processing subsystem 108. In an exemplary embodiment, the communication network may include, but is not limited to Bluetooth ™. In another exemplary embodiment of the present invention the communication network 106 may include, but is not limited to, a wire or a logical connection over a multiplexed medium, such as, a radio channel in telecommunications and computer networking. The examples of telecommunications and computer networking may include a local area network (LAN), a metropolitan area network (MAN) , a wide area network (WAN) or any wired or wireless network. [0025] In an embodiment of the present invention, the gravity data processing subsystem 108 is configured to compute bouguer anomaly values, gradient anomaly values and residual anomaly values using the gravity field data measured by the gravity meter 102 and the 3-D positioning data generated by the GNSS receiver unit 104 for identification of hydrocarbon provinces. The gravity data processing subsystem 108 is further configured to identify high gradient and low density zones for identification of hydrocarbon bearing zones. The gravity data processing subsystem 108 is explained in detail in later part of the specification. [0026] FIG. 2 illustrates a detailed block diagram of the gravity data processing subsystem 108 for identification of petroleum provinces through microgravity, in accordance with an embodiment of the present invention. In an embodiment of the present invention, the gravity data processing subsystem 108 comprises a computation engine 118, a processor 120 and a memory 122. In an exemplary embodiment of the present invention, the computation engine 118 may be implemented in a cloud computing architecture in which data, applications, services, and other resources are stored and delivered through shared data-centres. The computation engine 118 has multiple units that are configured to work in conjunction with each other for determining an optimal solution to computation problem with respect to the processing of the gravity data. The various units of the computation engine 118 are operated via the processor 120 specifically programmed to execute instructions stored in the memory 122. [0027] The computation engine 118 comprises a data collection unit 110, a data processing unit 112, a data filtering unit 114 and an identification unit 116. In an embodiment of the present invention, the data collection unit 110 receives the gravity field data from the gravity meter 102 and also receives 3-D positioning data obtained from a plurality of GNSS receiver units 104 via the communication network 106. In another embodiment of the present invention, the data collection unit 110 receives the gravity field data in raw form for further processing. [0028] In an embodiment of the present invention, the data processing unit 112 receives the gravity field data and 3D positioning data from the data collection unit 108 and computes the bouguer anomaly values from the gravity field data and the 3D-positioning data. In an embodiment of the present invention, the data processing unit 112 is further configured to compute a theoretical gravity data from a standard formula. The standard formula for computing the theoretical gravity is: g(cp) = ge (1 + A sin2 (