Abstract
Determining the reliable values of the filtration parameters of productive reservoirs is the most important task in monitoring the processes of reserve production. Hydrodynamic studies of wells by the pressure build-up method, as well as a modern method based on production curve analysis (Decline Curve Analysis (DCA)), are some of the effective methods for solving this problem. This paper is devoted to assessing the reliability of these two methods in determining the filtration parameters of terrigenous and carbonaceous productive deposits of oil fields in the Perm Krai. The materials of 150 conditioned and highly informative (obtained using high-precision depth instruments) studies of wells were used to solve this problem, including 100 studies conducted in terrigenous reservoirs (C1v) and 50 carried out in carbonate reservoirs (C2b). To solve the problem, an effective tool was used—multivariate regression analysis. This approach is new and has not been previously used to assess the reliability of determining the filtration parameters of reservoir systems by different research methods. With its use, a series of statistical models with varying degrees of detail was built. A series of multivariate mathematical models of well flow rates using the filtration parameters determined for each of the methods is constructed. The inclusion or non-inclusion of these filtration parameters in the resulting flow rate models allows us to give a reasonable assessment of the possibility of using the pressure build-up method and the DCA method. All the constructed models are characterized by high statistical estimates: in all cases, a high value of the determination coefficient was obtained, and the probability of an error in all cases was significantly less than 5%. As applied to the fields under consideration, it was found that both methods demonstrate stable results in terrigenous reservoirs. The permeability determined by the DCA method and the pressure build-up curve does not control the flow of the fluid in carbonate reservoirs, which proves the complexity of the filtration processes occurring in them. The DCA method is recommended for use to determine the permeability and skin factor in the conditions of terrigenous reservoirs.
Highlights
The main idea of the used approach is as follows. It is known from the theory of underground hydromechanics that the filtration parameters of productive formations significantly affect the flow of fluid and, as a result, can be used as input data in individual models for determining the flow rates of wells
When using the values determined during the processing of the pressure build-up curve as filtration parameters, the multivariate model of the fluid flow rate has the following form: For terrigenous reservoirs: m − pbc
When using the values determined during Decline Curve Analysis (DCA) processing as filtration parameters, the multivariate model of the fluid flow rate has the form:
Summary
Determination of the reliable values of the filtration parameters for productive reservoirs is the most important task in monitoring the production processes at hydrocarbon reserves. One of the effective methods for solving this problem is hydrodynamic studies of wells by the pressure build-up method. Hydrodynamic studies of wells, as a method for determining the filtration parameters of productive formations, are characterized by some disadvantages. In the conditions of oil production from low-permeable reservoirs, the pressure build-up process takes a long time, and the wells are put into operation without waiting for the full recovery of the bottom-hole pressure to the reservoir value [2]. Only in 10% of studies conducted at wells that operate low-permeability reservoirs in the Perm Region, the pressure in the well is completely restored. The use of modern software products, such as the Kappa Workstation software (Saphir module), for processing not fully recovered data, leads to difficulties, for example, in identifying a section of radial flow or other characteristic areas on diagnostic graphs [3,4]
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