Shandrygolov Z.N., Gumerova N.V., Kurin K.K and Morev M.A Industrial University of Tyumen, Volodarskogo, 38, Tyumen, Russia,

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 12, December 2018, pp , Article ID: IJCIET_09_12_093 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed A METHOD FOR CORRECTING PERMEABILITY AND POROSITY OF A HYDRODYNAMIC MODEL OF A GAS DEPOSIT BASED ON ANALYZING THE DYNAMICS OF THE RISE OF GAS-WATER CONTACT Shandrygolov Z.N., Gumerova N.V., Kurin K.K and Morev M.A Industrial University of Tyumen, Volodarskogo, 38, Tyumen, Russia, ABSTRACT Analysis of the results of adaptation made it possible to note the need to improve and refine the auto-adaptation algorithm for the targeted change of the interlayers studied, considering the historical dynamics of the GWC advance A detailed examination of the results of periodic measurements of GWC in the observation wells of Cenomanian deposits led to the conclusion that when developing a deposit, advance of GWC is not always even. The reason is not only in the different intensity of selection throughout the development history but also in the different permeability and porosity of the interlayers. Keywords: GWC advance, gas reservoir model Cite this Article: Shandrygolov Z.N., Gumerova N.V., Kurin K.K and Morev M.A, a Method for Correcting Permeability and Porosity of a Hydrodynamic Model of a Gas Deposit Based On Analyzing the Dynamics of the Rise of Gas-Water Contact, International Journal of Civil Engineering and Technology, 9(12), 2018, pp INTRODUCTION Adaptation of the rise of gas-water contact (GWC) in the hydrodynamic models of giant gas deposits is one of the most important parameters that are monitored when assessing the quality of the gas reservoir model. Proper reproduction of water injection into the reservoir is a task that requires a competent evaluation of the processes occurring in the formation. The method of adaptation described in [1] made it possible to set up a fund of production wells for actual measurements, using information on the latest study carried out. In a retrospective analysis of the dynamics of water injection along the wells in a group of deposits with greater average number of permeable intervals in the section and lithological heterogeneity; deviations in some editor@iaeme.com

2 Shandrygolov Z.N., Gumerova N.V., Kurin K.K and Morev M.A time zones were detected. Analysis of the results of adaptation made it possible to note the need to improve and refine the auto-adaptation algorithm for the targeted change of the interlayers studied, considering the historical dynamics of the GWC advance A detailed examination of the results of periodic measurements of GWC in the observation wells of Cenomanian deposits led to the conclusion that when developing a deposit, advance of GWC is not always even. The reason is not only in the different intensity of selection throughout the development history but also in the different permeability and porosity of the interlayers. The parameter of vertical permeability has the greatest uncertainty in terms of permeability and porosity, since its value is affected not only by the anisotropy coefficient of the formation, but also by the value of lateral permeability. Anisotropy in oil reservoirs is usually analyzed with the help of core studies, however, the core of the deposits, at which gas production is mainly carried out in the territory of Western Siberia, is practically not studied by this parameter. Anisotropy also differs in different classes of rocks that make up the Cenomanian deposit (sandstones, coarse-grained and fine-grained siltstones), which further complicates the task of determining vertical permeability. In addition, well log interpretation results subject to inaccuracies have a greater share of uncertainty in lateral permeability. A complex of the above factors directly affects the quality of the initial model, therefore, to obtain realistic forecast indicators, correction of variable parameters is required. The method proposed in this article allows identifying zones with parameters that need to be adjusted. For the GWC level of liquid from the aquifer to rise it is necessary to overcome cells lying below the current GWC position; they will be corrected (Figure 1). When adapting the model where the aquifer model cells are buried deeper than the initial GWC level, it is also recommended to consider the permeability adjustment in the area from the initial GWC level to the cells that are connected to the model. Figure 1 Diagram of permeability and porosity adjustment The method proposed in this article considers the actual value of the velocity of water rise in a given interval. So, proceeding from the physical meaning: υ = dh GWC dt, (1) editor@iaeme.com

3 A Method for Correcting Permeability and Porosity of a Hydrodynamic Model of a Gas Deposit Based On Analyzing the Dynamics of the Rise of Gas-Water Contact Where υ GWC velocity of GWC rise, m/year; DH difference between actual GWC position marks, m; dt time interval between measurements, year. In this case, the resulting velocity will be the estimated parameter for each cell, because the depth value of any adjustable interlayer will be between existing GWC measurements. In addition, the identified velocity will be the tangent of the slope of the straight line drawn through the selected measurements, from which it is possible to find the correction coefficient, as described in [1]. To determine the correction coefficient of permeability for the formation interval, a relationship is proposed that allows varying the factors in a predetermined interval. The result of the calculation by formula (2) will fall in the range from 0.37 to dh f dhm k = exp, dh (2) f Where k correction coefficient for the formation interval; dhm difference in marks between measurements by model; dhf difference in marks between measurements on fact. According to formula (1), it is possible to estimate the current model calculation, where for the correction, formula (2) can be used within the current adaptable interlayer. Such an approach will allow for a greater degree of consideration for permeability and porosity of the adjusted interval, reducing the number of iterations during the creation of the model, so it is used for implementation in the software. We should note the variability of the aquifer model distribution in relation to the connected cells, using the example of the Fetkovich aquifer [1]. In some simulators, a uniform distribution of the intensity of water injection into the deposit is realized, regardless of the geometric and filtration parameters of the connected cells. If you need to take into account such parameters, this simulator allows you to assign individual weight factors - multipliers of the intensity of water injection into certain cells. In other simulators, it is possible to connect the aquifer model using the weighting method by the area of the edge of the connected cell, or by its permeability. Such differences can significantly affect the distribution of water injection into the formation (Figure 2), which must be taken into account when reproducing the GWC rise. When using the weighting method by the connected cell permeability, it is possible to control the distribution of the intensity of water injection from the aquifer model, thereby obtaining a tool for adapting watercut to the level of the first GWC measurement. Figure 2 Example of various water injections using the weighting method of the connected cell permeability editor@iaeme.com

4 Shandrygolov Z.N., Gumerova N.V., Kurin K.K and Morev M.A For adaptation in the software without weighing the parameters of the connected cells, a separate algorithm was created, aimed at the primary balance of water distribution from the aquifer relative to the wells. After determining the required multipliers by formula (1), the geometric mean of the permeability per well is analyzed. This parameter is used to adjust the multiplier of the intensity of the aquifer inflow. The closer the geometric mean from the measurements in the well to one, the more accurately the rise is adjusted without the use of permeability multipliers (formula 3). n g P k = i i= 1 1/ n Where ki correction coefficient for the formation interval; n Number of adaptable GWC measurements; g Aquifer intensity multiplier for the connected cell. Such a consistent approach eliminated permeability distortion, caused by a shortage of incoming water. After adaptation of the aquifer, permeability is changed to refine the dynamics of the GWC rise with respect to each measurement, since adapting only aquifer multipliers in most cases does not accurately reproduce the dynamics of the rise. For use in practice, permeability adaptation was used at values from 0.9 to 1.1. An example of the successful application of the technique is shown in Fig. 3. (3) Figure 3 Example of well adaptation by different methods An example of the distribution of g multipliers as a function of the number of iterations can be seen in Figure 4. Convergence is achieved using the scaling function, so even after many iterations, it is not possible to exceed the minimum and maximum permeability limits established by the petrophysical dependence for a given well editor@iaeme.com

5 A Method for Correcting Permeability and Porosity of a Hydrodynamic Model of a Gas Deposit Based On Analyzing the Dynamics of the Rise of Gas-Water Contact Figure 4 Example of the result of calculating g multiplier in the adaptation of the wells of the Gubkinskoye oil and gas condensate field. In the course of creating the algorithm based on the GWC rise rate analysis method, an approach based on the adjustment of the original petrophysical model was implemented. Accounting for the dependence of implementation on the use of simulator options is made, a variant of the successive adaptation of the GWC rise is proposed, based on the field data. Implementation of the described method in the software product made it possible to shorten the adaptation time of the hydrodynamic models of the Cenomanian deposits of Western Siberia. The solution of the problem of adaptation of the GWC rise considering all the measurements made at the wells allowed improving the quality of the forecast parameters for the reservoir pressure, the GWC rise, and also most accurately predict the time of decommissioning of the wells due to watercut. The optimization algorithm made it possible to eliminate the non-systematic revaluation of the formation permeability, thereby improving the simulation quality. The described algorithm is used in the implementation of projects for the development of gas fields for solving the problems of non-correspondence of model values to actual measurements of GWC marks. REFERENCES: [1] Shandrygolov Z.N., Arkhipov Yu.A., Gumerova N.V., Kurin K.K., Morev M.V. Method of adaptation of gas-water contact of gas fields. News of higher educational institutions. Oil and gas, No. 4. Pp [2] Fetkovich, M.J A Simplified Approach to Water Influx Calculations-Finite Aquifer Systems. J Pet Technol 23 (7): SPE-2603-PA editor@iaeme.com