Incorporating Geomechanics into the Decline-Curve Analysis of Naturally Fractured Reservoirs

2011 ◽  
Author(s):  
Hadi Jabbari ◽  
Zhengwen Zeng ◽  
Mehdi Ostadhassan
Keyword(s):  
Fractured Reservoirs ◽  
Curve Analysis ◽  
Naturally Fractured Reservoirs ◽  
Decline Curve Analysis ◽  
Decline Curve ◽  
Naturally Fractured

Estimating the properties of naturally fractured reservoirs using rate transient decline curve analysis

2017 ◽  
Vol 28 (5) ◽  
pp. 848-856 ◽  
Author(s):  
Amin Daryasafar ◽  
Mohammad Joukar ◽  
Mohammad Fathinasab ◽  
Giovanni Da Prat ◽  
Riyaz Kharrat
Keyword(s):  
Fractured Reservoirs ◽  
Curve Analysis ◽  
Naturally Fractured Reservoirs ◽  
Decline Curve Analysis ◽  
Decline Curve ◽  
Naturally Fractured

Decline Curve Analysis Using Type Curves for Two-Porosity Systems

1981 ◽  
Vol 21 (03) ◽  
pp. 354-362 ◽  
Author(s):  
Giovanni Da Prat ◽  
Heber Cinco-Ley ◽  
Henry Ramey
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Skin Effect ◽  
Curve Analysis ◽  
Fractured Reservoir ◽  
Type Curve ◽  
Decline Curve Analysis ◽  
Decline Curve ◽  
Wellbore Storage ◽  
Naturally Fractured

Abstract Constant producing pressure solutions that define declining production rates with time for a naturally fractured reservoir are presented. The solutions for the dimensionless flow rate are based on a model presented by Warren and Root. The model was extended to include constant producing pressure in both infinite and finite systems. The results obtained for a finite no-flow outer boundary are new and surprising. It was found that the flow rate shows a rapid decline initially, becomes nearly constant for a period, and then a final decline in rat,- takes place.A striking result of the present study is that ignoring the presence of a constant flow rate period in a type-curve match can lead to erroneous estimates of the dimensionless outer radius of a reservoir. An example is presented to illustrate the method of type-curve matching for a naturally fractured system. Introduction Naturally fractured reservoirs consist of heterogeneous porous media where the openings (fissures and fractures) vary considerably in size. Fractures and openings of large size form vugs and interconnected channel, whereas the tine cracks form block systems which are the main body of the reservoir (Fig. 1). The porous blocks store most of the fluid in the reservoir and are often of low permeability, whereas the fractures have a low storage capacity and high permeability. Most of the fluid flow will occur through the fissures with the blocks acting as fluid sources. Even though the volumetric average permeability in a naturally fractured system is low, such systems often exhibit an effective permeability that is higher than the block matrix permeability, and behave differently from ordinary homogeneous media. These systems have been studied extensively in the petroleum literature. One of the first such studies was published by Pirson in 1953. In 1959, Pollard presented one of the first pressure transient models available for interpretation of well test data from two-porosity systems. The most complete analysis of transient flow in two-porosity systems was presented in 1960 by Barenblatt and Zheltov. The Warren and Root study in 1963 is considered the forerunner of modern interpretation of two-porosity systems. Their paper has been the subject of study by many authors. The behavior of fractured systems has long been a topic of controversy Many authors have indicated that the graphical technique proposed by Pollard in 1959 is susceptible to error caused by approximations in the mathematical model. Nevertheless, the Pollard method still is used. The most complete study of two-porosity systems appears to be the Mavor and Cinco-Ley study in 1979. This study considers wellbore storage and skin effect, and also considers production, both at constant rate and at constant pressure. However, little information is presented concerning the effect of the size of the system on pressure buildup behavior.Although decline curve analysis is widely used, methods specific to two-porosity fractured systems do not appear to be available. It is the objective of this paper to produce and study decline curve analysis for a naturally fractured reservoir. The Warren and Root model was chosen as the basis for this work. Partial Differential Equations The basic partial differential equations for fluid flow in a two-porosity system were presented by Warren and Root in 1963. The model was extended by Mavor and Cinco-Ley to include wellbore storage and skin effect. SPEJ P. 354^

Pressure Transient and Decline Curve Behaviors in Naturally Fractured Vuggy Carbonate Reservoirs

2005 ◽  
Vol 8 (02) ◽  
pp. 95-112 ◽  
Author(s):  
Rodolfo Camacho Velazquez ◽  
Mario A. Vasquez-Cruz ◽  
Rafael Castrejon-Aivar ◽  
Victor Arana-Ortiz
Keyword(s):  
Fractured Reservoirs ◽  
Naturally Fractured Reservoirs ◽  
Carbonate Reservoirs ◽  
Primary Flow ◽  
Interconnected System ◽  
Secondary Porosity ◽  
Decline Curve ◽  
Proposed Model ◽  
Naturally Fractured ◽  
Flow Through

Summary This study presents a new way to model high secondary porosity, mainly vuggy porosity, in naturally fractured reservoirs. New solutions are presented for two cases, one in which there is no primary flow through the vugs (which is an extension of the Warren and Root model) and one in which the dissolution process of pore throats has created an interconnected system of vugs and caves. In both cases, there is an interaction between matrix, vug, and fracture systems. New insights are provided. Both pressure and production responses during transient and boundary-dominated flow periods are explored. In transient well tests, for the case in which there is no primary flow through the vugs, a change of slope could be present during the transition period. Thus, this study shows that slope ratios of 2:1 of an early- or late-time segment vs. a transition segment do not necessarily imply transient interaction between matrix and fractures. It is also shown that the presence of vugs and caves may have a definitive influence on decline-curve and cumulative production behaviors; therefore, it is necessary to incorporate vuggy porosity in the process of type-curve match. Finally, the use of the methodology obtained in this work is illustrated with synthetic and field examples. Introduction Most of the world's giant fields produce from naturally fractured and vuggy carbonate reservoirs that have complex pore systems, mainly because carbonate rocks are particularly sensitive to post-depositional diagenesis, including dissolution, dolomitization, and fracturing processes. Complete leaching of grains by meteoric pore fluids can lead to textural inversion, which may enhance reservoir quality through dissolution or occlude reservoir quality through cementation. Some works have classified carbonates on the basis of fabric-selective and nonfabric-selective pore types. The nonfabric-selective types are vugs and channels, caverns, and fractures. For the purpose of this work, no distinction is made on vugs, caverns, and channels, and they will be denoted by the term vugs. Thus, vugs may vary in size from millimeters to meters in diameter. Vugs are the result of carbonate and/or sulfate dissolution. From core observations, the matrix-porosity types adjacent to the vuggy zones are moldic, solution-enlarged microfractures and solution-enlarged intercrystalline. Thus, it is possible to have a permeability enhancement adjacent to the vuggy zones. Three porosity types (matrix, fractures, and vugs) are usually present in naturally fractured, vuggy carbonate reservoirs. The determination of permeability and porosity in vuggy zones from core measurements is likely to be pessimistic because of sampling problems. In areas lacking cores, openhole wireline logs may be used to help identify vuggy zones; however, vugs are not always recognized by conventional logs because of their limited vertical resolution. Vuggy porosity is common in many carbonate reservoirs, and its importance in the petrophysical and productive characteristics of a carbonate rock has been recognized by several works. Vugular porosity can be subdivided into connected and disconnected types. The effect of vugs on permeability is related to their connectivity. High permeability may be present in vuggy zones by solution enhancement of pore throats, which creates an interconnected system of vugs. The presence of high-porosity and high-permeability vuggy zones may diminish waterflood effectiveness and leave a large amount of bypassed oil in the lower-permeability matrix. One purpose of our work is to present a technique to identify high secondary porosity, mainly vuggy porosity. It has been observed in the literature that vugular zones strongly influence production performance. This reference addresses the problem of modeling vuggy naturally fractured reservoirs, allowing the possibility of primary flow through vugs, and develops a method to identify vuggy reservoirs on well tests and decline curves, evaluate porosity associated with vugs and fractures, and determine vuggy connectivity. The proposed model can be used in numerical simulators. Some comparisons between the results of analytical solutions derived in this work and those obtained with a numerical simulator, which uses the proposed model, are presented.

An Investigation of Pressure and Production Data Using Decline and Type Curve Analysis

2017 ◽  
Author(s):  
Arifur Rahman ◽  
Fatema Akter Happy ◽  
Mahbub Alam Hira ◽  
M. Enamul Hossain
Keyword(s):  
History Matching ◽  
Fractured Reservoirs ◽  
Curve Analysis ◽  
The Other ◽  
Production Data ◽  
Type Curve ◽  
Type Curves ◽  
Decline Curve Analysis ◽  
Decline Curve ◽  
Analysis Technique

Decline curve analysis is one of the most widely used production data analysis technique for forecasting whilst type curve analysis is a graphical representation technique for history matching and forecasting. The combination of both methods can estimate the reserves and the well/reservoir parameters simultaneously. The purpose of this study is to construct the new production decline curves to analyze the pressure and production data. These curves are constructed by combining decline curve and a type curve analysis technique that can estimate the existing reserves and determine the other well/reservoir parameters for gas wells. The accuracy of these parameter estimations depends on the quality and type of the pressure and production data available. This study illustrates the conventional decline curve that can be used to analyze the gas well performance data with type curves based on pseudo time function. On the other hand, log-log plots are used as a diagnostic tool to identify the appropriate reservoir model and analogous data trend. Pressure derivative and type curves are used to construct a radial model of the reservoir. In addition, Blasingame and Fetkovich type curves analysis are also presented in a convenient way. The decline curve analysis shows steady state production for a long time, then a decline is observed which indicates a boundary dominated flow. The Blasingame type curve matching points is going downward, which indicate the influence of another nearby well. The reservoir parameters that are obtained by using the decline curve and type curves analysis show a similar trend and close match for different approaches. These observations closely match results of different analysis. This analysis improves the likelihood of the results being satisfactory and reliable, though it changes with time until the end of the production period. This analysis technique can be extended to other type of well/reservoir system, including horizontal wells and fractured reservoirs.

Decline Curve Analysis of Fractured Reservoirs with Fractal Geometry

2006 ◽  
Author(s):  
Rodolfo Camacho Velazquez ◽  
Gorgonio Fuentes-Cruz ◽  
Mario Alberto Vasquez-Cruz
Keyword(s):  
Fractal Geometry ◽  
Fractured Reservoirs ◽  
Curve Analysis ◽  
Decline Curve Analysis ◽  
Decline Curve
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