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Abstract This paper presents a rigorous theoretical development of long term boundary-dominated flow solutions which involve direct coupling of the stabilized flow equation with the gas material balance equation. Due to the highly non-linear nature of the gas flow equation, pseudopressure and pseudotime functions have been used over the years for the analysis of production rate and cumulative production data. While the pseudopressure and pseudotime functions provide a rigorous linearization of the gas flow equation, these transformations do not provide direct solutions. In addition, the pseudotime function requires the average reservoir pressure history - which in most cases is simply not available. Our approach uses functional models to relate the viscosity-compressibility product with the reservoir pressure (p/z) profile. These models provide approximate, but direct, solutions for modelling gas flow during the boundary-dominated flow period. For convenience, the solutions are presented in terms of dimensionless variables and expressed as type curve plots. Other products of this work are explicit relations for p/z and Gp(t). These solutions can be easily adapted for field applications such as rate prediction. We also provide verification of our new flowrate and pressure solutions using numerical simulation results and we demonstrate the application of these solutions using a field example. Introduction This paper focuses on the development and application of semianalytic solutions for modelling gas well performance - with particular emphasis on production rate analysis using decline type curves. Our emphasis on decline curve analysis arises both from its utility in viewing the entire well history, as well as its familiarity in the industry as a straightforward and consistent analysis approach. More importantly, the approach does not specifically require reservoir pressure data (although pressure data are certainly useful). Decline curve analysis typically involves a plot of production rate, qg and/or other rate functions (e.g., cumulative production, rate integral, rate integral-derivative, etc.) versus time on a log-log scale. This plot is matched against a theoretical model, either analytically as a functional form, or graphically in the form of type curves. From this analysis formation properties are estimated. Production forecasts can then be made by extrapolation of the matched data trends. The specific formation parameters that can be obtained from decline curve analysis areโOriginal-gas-in-place (OGIP), โPermeability or flow capacity, and โThe type and strength of the reservoir drive mechanism. In addition, we can establishโThe future performance of individual wells, and โThe estimated ultimate recovery (EUR). Attempts to theoretically model the production rate performance of gas and oil wells date as far back as the early part of this century. In 1921, a detailed summary of the most important developments in this area was documented in the Manual for the Oil and Gas Industry. Several efforts were made over the years immediately thereafter, and probably the most significant contribution towards the development of the modern decline curve analysis concept is the classic paper by Arps, written in 1944. In this work Arps presented a set of exponential and hyperbolic equations for production rate analysis. Although the basis of Arps' development was statistical, and therefore empirical, these historic results have found widespread appeal in the oil and gas industry. The continuous use of these so-called "Arps equations" is primarily due to the explicit form of the relations, which makes them easy for practical applications.
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reserves Evaluation > Estimates of resource in place (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Production forecasting (1.00)
- (2 more...)
SPE Members Abstract Choosing the proper application is crucial to the success of any horizontal well. Many horizontal wells drilled in the past were technical successes and economic failures. Thousands of horizontal wells have been drilled in the last five years, but most have targeted oil reservoirs with relatively low permeability and high pressures. This paper considers the applicability of horizontal drilling to a large gas reservoir with high permeability and low pressures. More specifically, it discusses an approach for evaluating the economics of drilling such a well in the West Panhandle Field Introduction The various Panhandle Fields are made up of a very large gas reservoir with an associated smaller oil reservoir. The flrst wells were drilled in the 1920's and the fields have grown to cover portions of eight counties in the Texas Panhandle. The cumulative recorded production is approximately 1,250 MMBbls and 33,000 Bcf. A large amount of additional gas was flared in the early life of the field. initial reservoir pressure was approximately 430 psia. Today these fields are in an advanced stage of depletion. There are currently about 10,500 oil wells producing an average 1.7 BOPD and 9 Mcfd per well. There are also about 4,400 gas wells producing an average 100 Mcfd per well. Almost all portions of the reservoir are at less than 100 psia P. 115^
- North America > United States > Texas > Potter County (1.00)
- North America > United States > Texas > Wheeler County (0.82)
- North America > United States > Texas > Moore County (0.82)
- (5 more...)
- North America > United States > Texas > Anadarko Basin > Panhandle Field > Red Cave Formation (0.99)
- Asia > India > Andhra Pradesh > Bay of Bengal > Krishna-Godavari Basin > Block KGD6 > G-1 Well (0.89)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (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)
Abstract A performance analysis technique is presented which can be used to identify recompletion candidates in producing gas fields. Through geological description and a field case history, it is demonstrated that p/z versus cumulative production curves can be diagnostic tools in identifying inefficient completions or wellbore damage in a stratified reservoir system. It is also shown that these wells can be recompleted or redrilled to add significant incremental reserves which would have otherwise been abandoned. Previous theoretical work presented in the literature demonstrated that layered gas reservoirs producing without crossflow display non-linear p/z versus cumulative production curves. This paper presents field data which support that observation and concludes that the absence of this behavior in a stratified reservoir environment may be indicative of a recompletion candidate due to wellbore damage in one or more of the layers. A field case history is presented involving wells producing from the Mesaverde Group in the San Juan Basin of New Mexico. Wells which were originally completed with nitroglycerin were selectively recompleted to yield significant incremental reserves. These wells were identified by their linear p/z behavior in an area where theory and historical performance indicate a non-linear p/z curve should be present. The results of the recompletion program are presented. Introduction The Mesaverde Group is the most important producing horizon in the San Juan Basin. This group accounts for approximately half of the estimated ultimate recovery of the basin. Almost all of this production can be attributed to the Blanco Mesaverde Field of New Mexico and the Ignacio Blanco Field of Colorado. A common completion practice used on Mesaverde wells during the early to mid-1950's was to detonate a charge of nitroglycerin at the bottom of the well. Presumably, this placed the charge opposite the productive interval. The explosion fractured or rubbled the formation and increased both the initial flow capacity and ultimate recovery of the well. The standard procedure was to complete the entire Mesaverde Group open hole. In many cases, the result was a very inefficient completion due to the nature of the explosive technique and the length (500โ1000 feet) of the productive interval. Only the most porous sands directly opposite the charge were effectively opened to flow. The remaining sands in the upper portion of the open hole were not stimulated and, consequently, did not contribute significantly to the production of the well.
- North America > United States > New Mexico > San Juan County (0.54)
- North America > United States > Colorado > La Plata County (0.44)
- North America > United States > Colorado > Archuleta County (0.44)
- Geology > Rock Type > Sedimentary Rock (0.47)
- Geology > Sedimentary Geology (0.47)
- Geology > Geological Subdiscipline (0.46)
- North America > United States > New Mexico > San Juan Basin > Point Lookout Formation (0.99)
- North America > United States > New Mexico > San Juan Basin > Menefee Formation (0.99)
- North America > United States > New Mexico > San Juan Basin > Blanco Mesaverde Field > Mesaverde Formation (0.99)
- (4 more...)
- Well Completion > Completion Installation and Operations (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (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)
SPE Members Abstract This paper introduces a new family of type curves for advanced decline Curve analysis. The new type Curves are obtained by combining the dimensionless production rate and the dimensionless cumulative production on a single log-log scale. The new type curve offers two significant advantages:observed cumulative production data is much smoother than observed production rate data, making a match easier to obtain with the new type curve; and simultaneously matching both rate and cumulative production provides more confidence in the selection of the correct early- and late-time stems. Plotting functions are presented to allow the new curves to be used for both oil and gas wells produced at either constant or varying flowing bottomhole pressure. Use of tie new type curves is demonstrated for both simulated and field data. Introduction In 1973, Fetkovich proposed a dimensionless rate-time type curve for decline curve analysis of wells producing at constant bottomhole pressure. These type curves, shown in Fig. 1, were developed for slightly compressible liquids. These type curves combined analytical solutions to the flow equation in the transient region with empirical decline curve equations in the pseudo-steady state region. The analysis procedure provided estimates of formation permeability, k, and drainage radius, re, instead of the traditional decline curve analysis parameters qi and Di. This approach to decline curve analysis, now commonly referred to as "advanced decline curve analysis", has become widely used as a tool for formation evaluation and reserves estimation. Fetkovich et al. presented several case studies of the use of advanced decline curve analysis. Bourdet, et al. introduced the use of derivative type curves for transient well test analysis in 1983. By multiplying the, pressure derivative by the time, (or equivalently, by taking the derivative of pressure with respect to the natural log of time), they were able to display both the pressure and pressure derivative type curves on a single set of axes. They pointed out that a simultaneous match of the pressure and pressure derivative type curves provides a more reliable interpretation of pressure transient test data than a match of the pressure type Curve alone. Because of this advantage, recent pressure transient analysis papers have routinely included both pressure and pressure derivative type curves. The pressure derivative type curve suffers from at least one minor disadvantage in that the process of taking the derivative from measured data amplifies any noise inherent in the data. For this reason, Blasingame, Johnston, and Lee suggested using the pressure integral rather than the pressure derivative. This procedure has the advantage of reducing rather than increasing any noise in the data. Production data often contains much more noise than pressure transient test data, making application of rate derivative type curves of little value. However, rate integral, or cumulative, type curves, can reduce the effect of this noise and make analysis of production data more reliable. This paper presents cumulative type curves for wells producing a single phase fluid, from a finite, radial reservoir, at constant flowing bottomhole pressure. In addition, plotting functions are presented to allow the new type curves to be used with gas wells and with oil or gas wells producing at varying bottomhole pressures. In principle, the concept of the combination rate and cumulative type curve may be extended to hydraulically fractured wells, to wells in dual porosity systems,, or to wells in arbitrarily shaped drainage areas. Discussion Review of Fetkovich Decline Curves Fetkovich developed his type curves by combining an analytical solution to the flow equation, describing transient flow, with empirical decline curve equations describing pseudo-steady state or boundary dominated flow. The transient portion of tile Fetkovich type curve is based on an analytical solution to the radial flow equation for slightly compressible liquids with a Constant pressure inner boundary and a no flow oiler boundary. P. 91^
- 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)