A Physics-Based Method To Forecast Production From Tight and Shale Petroleum Reservoirs by Use of Succession of Pseudosteady States

2015 ◽  
Vol 18 (04) ◽  
pp. 508-522 ◽  
Author(s):  
M. S. Shahamat ◽  
L.. Mattar ◽  
R.. Aguilera
Keyword(s):  
Balance Equation ◽  
Transient Flow ◽  
Material Balance ◽  
Petroleum Reservoirs ◽  
Flow Equation ◽  
Production Data ◽  
Material Balance Equation ◽  
Gas Reservoirs ◽  
Initial Flow ◽  
Shale Reservoirs

Summary Analysis of production data from tight and shale reservoirs requires the use of complex models for which the inputs are rarely known. The same objectives can also be achieved by knowing only the overall (bulk) characteristics of the reservoir, with no need for all the detailed and rarely known inputs. In this study, we introduce the concept of continuous succession of pseudosteady states as a method to perform the analysis of production data. It requires few input data yet is based on rigorous engineering concepts, which works during the transient- as well as the boundary-dominated-flow periods. This method consists of a combination of three simple and well-known equations: material balance, distance of investigation, and boundary-dominated flow. It is a form of a capacitance/resistance methodology in which the material-balance equation over the investigated region represents the capacitance and the boundary-dominated-flow equation represents the resistance. The flow regime in the region of investigation (the areal extent of which varies with time during transient flow) is assumed to be pseudosteady state. This region is depleted at a rate controlled by the material-balance equation. The initial flow rate and flowing pressure are used to define the resistance, and the distance of investigation defines the capacitance. The capacitance and resistance are then used in a stepwise procedure to calculate the depletion and the new rates or flowing pressures. The method was tested, for linear-flow geometry, against analytical solutions for liquids and numerical simulations for gas reservoirs, exhibiting both transient and boundary-dominated flow. Excellent agreement was obtained, thus corroborating the validity of the method developed in this study. Two practical examples are provided to demonstrate the applicability of the methodology to forecast production from tight and shale petroleum reservoirs. The proposed method is easy to implement in a spreadsheet application. It indicates that complex systems with complicated mathematical (e.g., Laplace space) solutions can be represented adequately by use of simple concepts. The approach offers a new insight into production analysis of tight and shale reservoirs, by use of familiar and easy-to-understand reservoir-engineering principles.

scholarly journals Dynamic Material Balance Method for Estimating Gas in Place of Abnormally High-Pressure Gas Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Lixia Zhang ◽  
Yingxu He ◽  
Chunqiu Guo ◽  
Yang Yu
Keyword(s):  
High Pressure ◽  
Material Balance ◽  
Balance Method ◽  
Production Data ◽  
Reservoir Pressure ◽  
Material Balance Equation ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Material Balance Method ◽  
The Relationship

Abstract Determination of gas in place (GIP) is among the hotspot issues in the field of oil/gas reservoir engineering. The conventional material balance method and other relevant approaches have found widespread application in estimating GIP of a gas reservoir or well-controlled gas reserves, but they are normally not cost-effective. To calculate GIP of abnormally pressured gas reservoirs economically and accurately, this paper deduces an iteration method for GIP estimation from production data, taking into consideration the pore shrinkage of reservoir rock and the volume expansion of irreducible water, and presents a strategy for selecting an initial iteration value of GIP. The approach, termed DMBM-APGR (dynamic material balance method for abnormally pressured gas reservoirs) here, is based on two equations: dynamic material balance equation and static material balance equation for overpressured gas reservoirs. The former delineates the relationship between the quasipressure at bottomhole pressure and the one at average reservoir pressure, and the latter reflects the relationship between average reservoir pressure and cumulative gas production, both of which are rigidly demonstrated in the paper using the basic theory of gas flow through porous media and material balance principle. The method proves effective with several numerical cases under various production schedules and a field case under a variable rate/variable pressure schedule, and the calculation error of GIP does not go beyond 5% provided that the production data are credible. DMBM-APGR goes for gas reservoirs with abnormally high pressure as well as those with normal pressure in virtue of its strict theoretical foundation, which not only considers the compressibilities of rock and bound water, but also reckons with the changes in production rate and variations of gas properties as functions of pressure. The method may serve as a valuable and reliable tool in determining gas reserves.

scholarly journals An Optimization-Based Method for the Explicit Production Data Analysis of Gas Wells

2022 ◽  
Vol 9 ◽  
Author(s):  
Lixia Zhang ◽  
Yong Li ◽  
Xinmin Song ◽  
Mingxian Wang ◽  
Yang Yu ◽  
...  
Keyword(s):  
Data Analysis ◽  
Balance Equation ◽  
Gas Flow ◽  
Material Balance ◽  
Gas Production ◽  
Production Data ◽  
Variable Rate ◽  
Material Balance Equation ◽  
Gas Wells ◽  
Gas Reservoir

This work aims at the exploration of production data analysis (PDA) methods without iterations. It can overcome limitations of the advanced type curve analysis relying on the iterative calculation of material-balance pseudotime and current explicit methods reckoning on specific production schedule assumptions. The dynamic material balance equation (DMBE) is strictly proved by the integral variable substitution based on the gas flow equation under the boundary dominated flow (BDF) condition and the static material balance equation (SMBE) of a gas reservoir. We introduce the pseudopressure level function γ(p) and the recovery factor function R(p) to rewrite the DMBE in terms of observed variable Y and estimated variable Ye; then the PDA can be transformed into an optimization problem of minimizing the error between Y and Ye. An optimization-based method for the explicit production data analysis of gas wells (OBM-EPDA), therefore, is developed in the paper, capable of determining the BDF constant and gas reserves explicitly and accurately for variable rate and/or variable flowing pressure systems. Three stimulated cases demonstrate the applicability and validity of OBM-EPDA with small errors less than 1% for estimated values of both reserves and Y. Not second to previous studies, the field case analysis further proves its practicability. It is shown that the nonlinear relation of γ to R can be represented by a polynomial function merely dependent on the inherent properties of the gas production system even before sorting out the production data. The errors of observed variable Y provided by OBM-EPDA facilitate the data quality control, and the elimination of outliers not subject to the BDF condition improves the reliability of the analysis. For various gas systems producing whether at a constant rate, a constant bottomhole pressure (BHP), or under variable rate and variable BHP conditions, the proposed method gives insights into the well-controlled volume and production capacity of the gas well whether in a low-pressure or high-pressure gas reservoir, where the compressibilities of rock and bound water are considered.

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