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Abstract Pressure buildup test analysis has been used to investigate near wellbore environment, estimate reservoir pressure and reveal external reservoir boundary types. However, despite of these benefits no consideration has been given for the angle of inclination of the faults or boundaries within which the well is completed. The angle of inclination of the boundaries of a reservoir has a significant impact on the pressure behavior and performance of a well. Knowledge of the inclination angle of the faults assist in well placement for optimum production. The objective of this paper, therefore, is to develop a procedure for calculating the angle of a well completed within a pair of inclined sealing faults using pressure buildup test analysis. A well completed in an infinite-acting reservoir produces number of images inversely proportional to the angle of inclination and dependent on nature of the faults. This number of images, n, can also be related to the angle at which the faults are inclined. The principle of superposition is used to aggregate pressure drop history of a vertical shutin after a constant rate of production. Pressure buildup test procedure was developed from the total pressure expression following the rate history. The procedure considered fault angle and distances from an object well of every image formed because of the inclination of the sealing faults. The buildup test procedure developed shows linear partial variation of Horner ratio at early shutin time and late shutin time, assuming constant rate of production before shut in. The coefficient of the early time Horner's ratio is the early flow time slope. The late time Horner's ratio has coefficient which is the product of the early time slope and the number of images formed due to sealing faults angle. The result shows that that the model is only valid for long shutin time, and the second slope must be gotten at the late time region for higher accuracy. Finally, the procedure does not depend on well design or distances of the images from the object well. The analysis procedure developed here can be used to estimate the angle of inclination of two faults within which a well is completed. Near wellbore characterization is also possible. Decision on well location for optimum well production or injection can be made from the angle of inclination of the faults.
- Africa > Nigeria (0.47)
- North America > United States > Texas (0.28)
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
Characteristics of Dimensionless Pressure Gradients and Derivatives of Horizontal and Vertical Wells Completed within Inclined Sealing Faults
Ogbamikhumi, A V (Department of Petroleum Engineering, University of Benin Edo State - Nigeria) | Adewole, E S (Department of Petroleum Engineering, University of Benin Edo State - Nigeria)
Abstract Dimensionless pressure gradients and dimensionless pressure derivatives characteristics are studied for horizontal and vertical wells completed within a pair of no-flow boundaries inclined at a general angle โฮธโ. Infinite-acting flow solution of each well is utilized. Image distances as a result of the inclinations are considered. The superposition principle is further utilized to calculate total pressure drop due to flow from both object and image wells. Characteristic dimensionless flow pressure gradients and pressure derivatives for the wells are finally determined. The number of images formed due to the inclination and dimensionless well design affect the dimensionless pressure gradients and their derivatives. For n images, shortly after very early time for each inclination, dimensionless pressure gradients of 1.151(N+1)/LD for the horizontal well and 1.151(N+1) for vertical well are observed. Dimensionless pressure derivative of (N+1)/2LD are observed for central and off-centered horizontal well locations, and (N+1)/2 for vertical well are observed. Central well locations do not affect horizontal well productivity for all the inclinations. The magnitudes of dimensionless pressure drop and dimensionless pressure derivatives are maximum at the farthest image distances, and are unaffected by well stand-off for the horizontal well.
Abstract Type curves come in handy when our pressure buildup and pressure drawdown analysis do not yield a straight line hence generating a master curve for wells completed within a pair of sealing faults. The type curves from an observed data is superimposed on the master curve to estimate reservoir system properties. A sealing fault creates image wells, which communicate with each other and the object well. As a result, object well performance can be affected by reservoir boundaries, and positioning of a well therefore must be strategic to ensure oil production for a long time. This is because pressure drop across the producing well is the addition of the pressure drop of the object well and the several image wells created because of the inclination. This is the principle of superposition. The inclination of a sealing fault influences the number of image wells, n, with the model n = (360/ฮธ) -1. With different angles of inclination of the sealing faults, polygons are constructed to determine the distances between the object well and corresponding image wells. In this paper, both dimensionless pressure and dimensionless pressure derivatives type curves as functions of number of image wells, are produced assuming that a vertical well is completed within a pair sealing faults. Wellbore storage and skin effects are considered. The results provide distances for several angles of inclination. Object well design, image well distances and faults angle affect dimensionless pressure and dimensionless pressure derivative. Dimensionless pressure and dimensionless pressure derivative of 2.3026(n+1) per cycle and 0.5(n+1), respectively are observed. Generating dimensionless pressure derivative curves helps the engineer to identify the point where the hump expires and where the straight-line analysis begins. That is the right point for well test analysis.
- Africa > Nigeria (0.32)
- North America > United States > Texas (0.28)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Pressure transient analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
Dimensionless Pressures and their Derivatives for a Vertical Well Completed within a Pair of Inclined Constant-Pressure Boundaries
Ojukwu, I. N. (Department of Petroleum Engineering, University of Benin, Benin-City, Edo State, Nigeria) | Adewole, E. S. (Department of Petroleum Engineering, University of Benin, Benin-City, Edo State, Nigeria) | Taiwo, O. A. (Department of Petroleum Engineering, University of Benin, Benin-City, Edo State, Nigeria)
Abstract Dimensionless pressure and their derivatives assist tremendously in understanding the reservoir boundary types, efficient well design, completion and production scheduling for optimum recovery from the reservoir. For a reservoir boundary as inimical as constant-pressure to oil or gas production, the need to adequately anticipate its presence and approach pattern towards the wellbore cannot be overemphasized. In this paper, dimensionless pressures and their derivatives are provided for a vertical well completed within a pair of inclined constant-pressure boundary (CPB) support. The angle of inclination of the constant-pressure boundaries is varied between 0 and 360 degrees. Hence, a generalized dimensionless pressure and derivatives expressions are derived by superposition of dimensionless pressures of all image wells on one object well. Therefore, distances of every individual well from the object well and the sign of every image, taken through a counterclockwise direction from the object well, are major inputs into the dimensionless pressures and dimensionless pressure derivatives derived. Only the object wellbore skin but not its storage is considered. The solutions are plotted as type curves. Results show dependence of both dimensionless pressure and dimensionless derivatives on angle of inclination of the constant-pressure boundaries. The dimensionless pressures exhibit a unique gradient at late dimensionless times. There is a collapse of the derivatives to zero at late dimensionless times. The rapidity of the collapse depends on object well distance from the boundaries and the angle of inclination of the boundaries. Wells completed farther away from the CPBs exhibit unperturbed production for longer periods than nearer wells.
Abstract At inception of a production rate regime, a horizontal well is expected to sweep oil within its drainage radius until the flow transients are interrupted by an external boundary or an impermeable heterogeneity. If the interruption is an impermeable heterogeneity or sealing fault, then the architecture of the heterogeneity must be deciphered in order to be able to design and implement an effective work-over or well re-entry to boost oil production from the reservoir. In this paper, therefore, the behavior of a horizontal well located within a pair of sealing faults inclined at 90 degrees is investigated using flow pressures and their derivatives. It is assumed that the well flow pressure is undergoing infinite activity, and each fault acts as a plane mirror. The total pressure drop in the object well is calculated by superposition principle. Damage and mechanical skin and wellbore storage are not considered. The main objective of our investigation is to establish identifiable signatures on pressure-time plots that represent infinite flow in the presence of adjacent no flow faults inclined at 90degrees. Results obtained show that the flowing wellbore pressure is influenced strongly by object well design, object well distance from each fault, and distance of each image from the object well. Irrespective of object well distance from the fault, there are three (3) images formed. Central object well location yields a square polygon, with two image wells nearer to the object well at equidistance from the object well, and the farthest image well to be . From the object well For off-centered object well location within the faults, a rectangular polygon is formed, with each image at a different distance from one well to another. Dimensionless pressure and dimensionless pressure derivative gradients during infinite-acting flow are (4.6052/LD) and 2/LD, respectively for all well locations within the faults.