Title of Invention

THREE-DIMENSIONAL CORE HOLDER FOR PERFORMANCE EVALUATION OF OIL WELL CONFIGURATIONS

Abstract

A three-dimensional core holder for performance evaluation of oil well- configurations comprising: a cover with plurality of holes and a body housing a core; a stand to tilt the core holder, an optional means for locking the core holder at a given inclination, wherein the body comprises of multi-holed side-faces and a bottom-face with the cover and side-faces of the core holder mutually perpendicular or optionally at an angle with each other, the number of holes on the cover and the side-faces varying from 1 to n=(L-s)/(s+d), wherein L is the length of the cover/side-face, s is spacing between two consecutive holes and d is the diameter of the holes, the number of rows on the cover and the side-faces varying from 1 to m = (W-p)/(p+d), wherein W is the width of the cover/side-face, and p is the spacing between two consecutive rows, the rows being parallel or staggered; wherein the holes being equipped with selective connecting and disconnecting means interconnected to form a manifold with options to remove the entire manifold for a given row to function as a conduit for injecting and / or ejecting fluids from one or more holes along a given row and introducing sealant fluid and venting gases, wherein pressure measuring devices can be fitted in the holes on the body faces and the cover; thereby facilitating saturation of the core, providing means for selective placement of injection and production wells and permitting pressure measurements and sealing the core and the drainage of the sealant.

Full Text

FORM 2 THE PATENT ACT, 1970 (39 OF 1970) COMPLETE SPECIFICATION (See section 10; rule 13) TITLE OF INVENTION "Three-Dimensional Core Holder for Performance Evaluation of Oil Well Configurations" (a)INDIAN INSTITUTE OF TECHNOLOGY Bombay (b) having administrative office at Powai, Mumbai 400 076, State of Maharashtra, India and (c) an autonomous educational Institute, and established under the Institute of Technology Act 1961 and (a)OIL AND NATURAL GAS CORPORATION LIMITED (b) having registered office at Jeevan Bharti Tower II. 124 Indira Chowk, New Delhi 1100 01, India and (c) a company incorporated under the Companies Act 1956 The following specification particularly describes the nature of the invention and the manner in which it is to be performed. 2 MAY Z008 GRANTED Field of the Invention This invention relates to a three-dimensional core holder for performance evaluation of well-configurations for oil recovery. Background of Invention Oil exists deep below the earth's surface entrapped in porous structure, called reservoir formed by various natural formations. The reservoir spans over several square miles in area and several hundred meters in depth. Oil is recovered from the reservoir by displacing it with another immiscible/miscible fluid, which is introduced through wells bored into the reservoir. These well-configurations are either horizontal or vertical or a combination of them and the oil recovery performance from the reservoir depends on the strategic placement of the wells. The flow of fluids in the reservoir is three-dimensional because of the inherent reservoir heterogeneity and the placement of the wells in two perpendicular directions. To determine the strategy of oil recovery, a core sample is obtained from the reservoir and is placed inside a core holder maintained at high temperature and pressure. The core is then saturated with oil and water to levels close to those in the reservoir. Horizontal and vertical wells are placed at different locations within the core and the corresponding oil recovery is measured. Pressure measurements at various locations along the core are required to track the movement of the fluid front and fine-tune the oil recovery predictions of commercial numerical simulators. US Patent 4649737 discloses a method and apparatus for automatic testing of core samples wherein the apparatus is capable of measuring the permeability and porosity of multiple cores at a time. It has a piston for transferring the core sample from the carousel into the sample holder wherein the piston in co¬operation with the sample holder seals the core in a test chamber. US Patent 4753107 describes a core holder, which is designed for testing of geological cylindrical core samples. It is capable of subjecting the core to axial and radial pressure of equal or unequal magnitude at high temperature. US Patent 4710948 provides an improved design of a Geological Core holder with composite barrel permitting examination of the core holder under various pressure and temperature conditions by linear and computerized tomographic X-ray imaging. The core holder includes an elongated barrel constructed of composite of wound and longitudinally extending non-metallic fibers embedded in a resin matrix to provide a high strength structure which presents a minimal attenuation of X-rays and magnetic flux. US Patent 4537063 discloses a non steady state core holder that is capable of measuring permeability and other flow properties of the rock core sample under non-steady flow condition. U S Patent 5325723 describes a core sample test method and apparatus wherein a core sample from an oil and gas well can be quickly and easily inserted and removed from the core holder wherein it is tested for both longitudinal and lateral strain in response to applied strain. Both Longitudinal and lateral yield can be concurrently sensed and such sensing can be done under temperature up to 300o F. and radial and pore pressure up to about 10000 psi. Young's modulus and Poisson's ratio can be determined from the stain and stress information. US Patent 4996872 describes another modular core holder for testing core permeability includes a modular sleeve comprising a series of sleeve segments aligned longitudinally. It permits the sleeve length to be varied without changing the manufacturing process of the sleeve and without requiring an inventory of sleeves of different lengths, with a provision to vary the pressure within the sleeves. US Patent 2345935 provides a Method and Apparatus for Permeability Measurement in which the core holder is capable of measuring effective permeability's of rocks and other formations to the flow of fluids such as oil, water, and gas. The device is capable of measuring pressure with extremely small volume displacement. A constant flow rate can be maintained through the core by an improved pump operating on electro-osmotic principle. It is also possible, through the device, to measure the effect of capillary forces and other effects involved in reservoir pressure measurements. US Patent 4506542 describes an Apparatus and Procedure for Relative Permeability Measurements. This is an apparatus for determining the data from which the relative permeability of a porous body to first fluid and second fluid can be calculated. The device renders the first and second outer faces of the porous body impermeable to the first and second fluid. In the device, the first and second capillary barriers, respectively, covers the first and second outer surfaces of the porous body. The pressure of the first fluid downstream of the porous body and the flow rate of the first fluid are held constant while the saturation level of second fluid in the porous body is varied. Data obtained from pressure and flow rate information may be used to determine the relative permeability of the first and second fluids using Darcy's law. US Patent 4599891 discloses a TCH-Tri-Axial Core Holder that relates to the tri-axial core holder which includes a hollow housing preferably made of steel, having a resilient sleeve therein. Two independent pressure sources are provided to apply pressure on the caps of the core holder. Pressures can be independently applied at infinitely variable degrees of radial and longitudinal axial forces. A longitudinal axial force is applied on the core independently of the pressure applied radially to the core. The fluid pressure or flow rate is measured at the periphery of the core during the injection of the fluids. US Patent 5868030 deals with a Core Sample Test Method and Apparatus in which elastic properties of a core sample can be determined. The apparatus is for detecting changes in longitudinal and lateral dimensions and/or acoustic properties of the core sample. It allows the testing of multiple samples with a minimum of equipment disassembly and reassembly required between testing of samples. An acoustic measurement capability of the device allows the determination of the impact of stress loading on the dynamically derived mechanical property values. US Patents 4649737, 4753107, 4537063, 4996872, 2345935, and 4506542 describe measurement of relative permeability by using cylindrical core holders. None of them permit oil recovery studies with different well-configurations. It is clear that core holders disclosed in the prior art are cylindrical and are restricted for measurement of relative permeability only. Such measurement needs facility for saturating the core with the displaced/displacing fluid, which are readily done by injecting fluid from one end and collecting it from the other end of the cylinder. Such core holders do not have provisions for evaluation of fluid flow in the core (rock) along multiple directions. Therefore, a three-dimensional core holder is required with configurations for placement of horizontal and vertical pathways (wells) in the core. Such core holder should also enable saturation of the core sample and allow multi-point pressure measurement for determining the oil recovery strategy. The present invention overcomes the above-noted and other shortcomings of the prior art by providing a novel three-dimensional core holder. Summary of the Invention The main object of the present invention is to provide a three-dimensional core holder that permits fluid flow in a core with different well-configurations to enable performance evaluation of oil well-configurations. It is another object of the invention to provide a core holder that enables measurement of pressures at various locations on all faces of the core, to provide information to fine-tune theoretical predictions. It is yet another object of the invention to provide a core holder with the flexibility of putting injector and producer wells at different locations in the core to enables oil recovery studies for different well lengths. It is yet another object of the invention to provide a core holder to enable study on multi-lateral wells. It is yet another object of the invention to provide a core holder that can be positioned at any angle with the vertical axis to conduct studies on dip effect. It is yet another object of the invention to provide a core holder that can be used for loose material like sand and packed material like rock. Description of Figures Figure 1: Plan and elevation of core holder (a) Plan; (b) Elevation; (c) Side View; 1 - Holes for attaching the cover plate to the body; 2- Holes for valves Figure 2: Details of valve and manifold 1 - Manifold; 2- Swagelok Connector; 3 - body Figure 3: Schematic for packing sand in the core holder 1 - Cover plate with pre-dilled holes; 2- Blind sheet; 3- Teflon sheet; 4 - Core holder; 5 - Holes for attaching the cover plate to the body Figure 4: Core holder with the rocking stand 1 - Bottom face; 2 - Side face; 3 - flange; 4- Cover plate; 5 - Gasket; 6- Stand Figure 5: Measured pressure data Figure 6: Recovery curves for different well-configurations Detailed description of the Invention The core holder comprises of a cover [1 in Figure 3] and a body that houses the core. The cover [1 in Figure 3] has bored through holes. The body comprises of side-faces [2 in Figure 4] and one bottom-face [1 in Figure 4]. The cover and the side-faces of the core holder can be mutually perpendicular or at an angle with each other. The four side-faces also have bored through holes [1 in Figure 1], The number of holes on the cover and the side-faces can vary from one to n=(L-s)/(s+d), where L is the length of the cover/side-face, s is spacing between two consecutive holes and d is the diameter of the holes. The number of rows on the cover and the side-faces can vary from one tom = (W-p)/(p+d), where W is the width of the cover/side-face, and p is the spacing between two consecutive rows. The rows can be parallel or staggered. These holes allow the core to be saturated and provide means to for selective placing of injection and production wells. Holes also permit pressure measurements. To investigate dip effect, the core holder can rest on a stand [6 in Figure 4] that can be tilted. This feature also helps in sealing the core and the drainage of the sealant, where applicable. An embodiment of the core holder is shown in Figure 1. The core holder comprises of a cover plate [1 in Figure 3] and the body [3 in Figure 2] that houses the core. The core holder rests on a stand [6 in Figure 4] mounted on a flat-platform fitted with wheels for mobility. Figure 1a shows the top view of the cover plate, which has multiple rows of holes with multiple number of holes [2 in Figure 1a] in each row, preferably three rows of holes with five holes in each row. Holes provide access for the injection and production wells. Each hole is fitted with a nut connected to a male connector [2 in Figure 2] at the end of this nut. A tube connects the connector to an on-off valve. The outlet of the valves in each row is connected to a common manifold [1 in Figure 2]. This manifold is a common conduit for either injecting or producing fluids from one or more holes along a given row. The holes meant for injection/production wells have their valves in on-position, rest are kept in off-position. The connector [2 in Figure 2] allows a particular valve to be disconnected from the manifold so that a pressure transmitter is mounted on the hole and a blind is fitted to the corresponding open-end of the manifold. The design allows the flexibility of removing the entire manifold for a given row. The top plate also has four holes [1 in Figure 1a], one at each corner (with provision of blinds), out of which two are used for pouring the sealant fluid and the remaining two are kept for the gas vent. The body comprises a bottom face [1 in Figure 4] and four side-faces [2 in Figure 4], which are welded to the bottom face on its four edges. Figures 1b and 1c show array of holes on a side-face of the embodiment. Each of the holes on the four faces has nut, connector, and valve arrangement as holes on the cover plate and all valves in a row are connected to a common manifold [1 in Figure2]. The cover plate [1 in Figure 3] is attached to the main body by means of studs placed along the periphery of the cover plate, as shown in Figure 4. A gasket [5 in Figure 4] is placed in between the cover plate and the main body to eliminate leakage. Sand pack, sand-stone block or limestone block taken from outcrops are the porous media on which unconventional flood patterns are studied. For testing on sand packs, blind plates [2 in Figure 3] are inserted between the cover plate and sand. The over-burden is applied by appropriate tightening of studs. A Teflon sheet [3 in Figure 3] is placed on top of the sand to avoid any leakage of water. Both the blind plates and Teflon sheet have pre-drilled holes [5 in Figure 3] aligned with the valve positions of the cover plate, as shown in Figure 3. For testing of rock samples, blind plates and Teflon sheet arrangement is not needed. The entire assembly of the core holder is mounted on a rocking stand [6 in Figure 4], which can be tilted on either side (Figure 4). This allows the uniform flow and distribution of the sealant in the gap between the sample and the core holder. The core holder can be tilted to a given angle and locked in that position to study dip effect. The entire core holder with rocking stand is mounted on a base with four wheels for easy movement of the core holder. To evaluate the performance of oil well-configurations, the porous medium is placed in the core holder and made leak proof by inserting blind plates between the cover plate and test sample optionally with a sealing sheet such as a Teflon sheet placed on its top surface to avoid any leakage of water, the said blind plates and said teflon sheet having pre-drilled holes aligned with the valve positions of the cover plate, applying over-burden by tightening of studs; the core is uniformly saturated by inserting the fluid into the manifold; injection and production wells are selectively placed to perform oil recovery studies; pressure is measured by means of pressure transmitters mounted on the appropriate holes on the cover plate and the body; the core holder is fixed at an angle with vertical by means of stand and locking mechanism. Figure 5 shows representative pressure measurements at few locations on the core. Figure 6 shows representative performance of two oil well-configurations (Vertical Injection-Vertical Production, Vertical Injection-Horizontal Production) in terms of oil recovery as a function of amount of fluid injected. Claims We claim: 1. A three-dimensional core holder for performance evaluation of oil well- configurations comprising: a cover with plurality of holes and a body housing a core; a stand to tilt the core holder, an optional means for locking the core holder at a given inclination, wherein the body comprises of multi-holed side-faces and a bottom-face with the cover and side-faces of the core holder mutually perpendicular or optionally at an angle with each other, the number of holes on the cover and the side-faces varying from 1 to n=(L-s)/(s+d), wherein L is the length of the cover/side-face, s is spacing between two consecutive holes and d is the diameter of the holes, the number of rows on the cover and the side-faces varying from 1 to m = (W-p)/(p+d), wherein W is the width of the cover/side-face, and p is the spacing between two consecutive rows, the rows being parallel or staggered; wherein the holes being equipped with selective connecting and disconnecting means interconnected to form a manifold with options to remove the entire manifold for a given row to function as a conduit for injecting and / or ejecting fluids from one or more holes along a given row and introducing sealant fluid and venting gases, wherein pressure measuring devices can be fitted in the holes on the body faces and the cover; thereby facilitating saturation of the core, providing means for selective placement of injection and production wells and permitting pressure measurements and sealing the core and the drainage of the sealant. 2. A three-dimensional core holder as claimed in claim 1 wherein the core holder comprises a cover plate and the body housing a core, the said core holder resting on a stand mounted on a platform fitted with devices for mobility such as wheels, rollers and the said cover plate, having three rows of holes wherein each row has five holes to provide access for the injection and production wells, wherein, each hole is fitted with a nut connected to a male connector at its distant end with a connecting tube with an on-off valve, the outlet of the said valves opening to a common manifold acting as a common conduit for either injecting or producing fluids from one or more holes along a given row; the said connecting tube permitting selective connection/disconnection of a valve from the said manifold which has a pressure transmitter mounted on the hole and a blind fitted to the corresponding open-end of the manifold, with the option of removing the entire manifold for a given row. 3. A three-dimensional core holder as claimed in claims 1 and 2 wherein the cover plate has four holes, one at each corner with provision of blinds, of which two holes are used for pouring the sealant fluid and the other two used for gas venting. 4. A three-dimensional core holder as claimed in claims 1-3 wherein spacers are provided on the inside of the four side-faces and the bottom plate to provide gap for the flow of sealing fluid . 5. A three-dimensional core holder as claimed in claims 1-4 wherein the cover plate is attached to the main body by means of studs placed along the periphery of the cover plate and a gasket is placed in between the cover plate and the main body to eliminate leakage. 6. A three-dimensional core holder as claimed in claims 1-5 wherein the core holder is capable of containing loose or compact materials for testing. 7. A three-dimensional core holder as claimed in claims 1-6 wherein the loose material is sand and the compact material is rock 8. A three-dimensional core holder as claimed in claims 1-6 wherein the oil well-configurations evaluation comprises: • inserting blind plates between the cover plate and test sample optionally with a sealing sheet such as a Teflon sheet placed on its top surface to avoid any leakage of water, the said blind plates and said teflon sheet having pre-drilled holes aligned with the valve positions of the cover plate, applying over-burden by tightening of studs; • saturating the core uniformly by inserting the fluid into the manifold; • selectively placing injection and production wells to perform- oil recovery studies; • measuring pressure by means of pressure transmitters mounted on the appropriate holes on the cover plate and the body, • fixing the core holder at an angle with vertical by means of stand and locking mechanism. Dated: 01/02/2006 DR. Prabuddha Ganquli Agent on behalf of Applicants

Documents:

1463-mum-2005-cancelled pages(2-5-2008).pdf

1463-mum-2005-claims(granted)-(02-05-2008).doc

1463-mum-2005-claims(granted)-(2-5-2008).pdf

1463-mum-2005-correspondence(ipo)-(31-10-2008).pdf

1463-mum-2005-correspondence1(23-11-2005).pdf

1463-mum-2005-correspondence2(2-5-2008).pdf

1463-mum-2005-drawing(2-5-2008).pdf

1463-mum-2005-form 1(24-11-2005).pdf

1463-mum-2005-form 18(19-10-2006).pdf

1463-mum-2005-form 18(31-12-2007).pdf

1463-mum-2005-form 2(granted)-(02-05-2008).doc

1463-mum-2005-form 2(granted)-(2-5-2008).pdf

1463-mum-2005-form 26(31-12-2007).pdf

1463-mum-2005-form 26(9-11-2005).pdf

1463-mum-2005-form 3(31-12-2002).pdf

1463-mum-2005-form 5(1-2-2062).pdf

1463-MUM-2005-FORM 8(15-5-2008).pdf

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