Performance of Finite-Conductivity, Vertically Fractured Wells in Single-Layer Reservoirs

Abstract

Summary Although even a perfunctory survey of the literature suggests that considerable information is available on the response of finite-conductivity fractures in single-layer systems, the influence of the settling of propping agents and the effect of fracture height on the well response need to be examined. These topics are examined in this paper. We suggest methods to analyze well performance when the fracture paper. We suggest methods to analyze well performance when the fracture conductivity is a function of fracture height and fracture length. The performance of wells with fracture height greater than the formation performance of wells with fracture height greater than the formation thickness is documented. The consequences of being unable to contain the fracture within the pay zone are also examined. Although incidental to this study, we found that solutions presented by various authors are not in agreement for all time ranges. In this paper, we discuss a systematic procedure to obtain a grid (mesh) so that paper, we discuss a systematic procedure to obtain a grid (mesh) so that accurate results are obtained by a finite-difference model. This procedure can be used for both two-dimensional (2D) and three-dimensional (3D) problems. problems. Introduction This paper examines the performance of wells intercepting finite-conductivity vertical fractures. Although much work has been presented in this area of pressure analysis, several aspects of well behavior have yet to be examined. We examine some of these topics. In this work we examine the influence of vertical variations in fracture conductivity on well performance. Concerns regarding the effect of the settling of propping agents on well productivity addressed in this paper complement our work on the influence of lateral variations in fracture conductivity. We also examine situations where the fracture extends below and/or above the productive interval. We consider two possibilities:the fracture length is assumed to be fixed and the fracture height is variable (volume of fracture treatment is variable); andthe fracture volume is assumed to be fixed (the product of the fracture half-length and fracture height is assumed to be constant). The latter case is of interest if one is not able to contain the fracture within the pay zone of interest. In the former case, we show that this approach provides a means to increase the effective fracture conductivity. These topics have not previously been examined in the literature. Verification of the finite-difference model used in this study consumed a significant portion of the time spent in this study. Although some works have reported problems in obtaining accurate solutions, no guidelines for choosing a grid (mesh) for this problem are available. We give empirical guidelines for systematically choosing a grid to obtain accurate solutions. We believe that these guidelines will significantly reduce the time spent by researchers in developing their own models and consider it an important contribution. We also present methods to modify grids developed for a given set of conditions if the fracture and/or reservoir dimensions are changed.

Pressure-transient analysis of infinite-conductivity fractured gas wells producing at high-flow rates

“…This permits accurate modeling of the flow behavior during the fracture and formation linear-flow periods. The grid architecture used in this study is identical to those used by Morse and Von Gonten (1972), Agarwal et al (1979a,b), Bennett et al (1986), Settari et al (2000), Nashawi (2006), and Nashawi and Malallah (2007). Fig.…”

“…In 1960, McGuire and Sikora used an electronic-analog computer model to study the effect of vertical fractures on fractured well performance. Since then, with the advent of the computer era, many advanced numerical solutions addressing well test analysis of fractured oil wells appeared in the well testing literature (Russell and Truitt, 1964a,b;Raghavan et al, 1972a,b;Locke and Sawyer, 1975;Agarwal et al, 1979a,b;Narasimhan and Palen, 1979;Bennett et al, 1982Bennett et al, , 1986Ding, 1996). Subsequently, the numerical models were followed by many semi-analytical solutions (Prats, 1961;Prats et al, 1962a,b;Gringarten and Ramey, 1973a,b;Gringarten et al, 1975a,b;Samaniego, 1977, 1981a;Hanley and Bandyopadhyay, 1979;Lee and Brockenbrough, 1986).…”

Long-Term Performance of Hydraulically Fractured Layered Rich Gas Condensate Reservoir

“…Only one-fourth of the drainage area is modeled because of the symmetry. The grid system is generated according to the guidelines proposed by Bennett et al (1986). Detailed investigations were first carried out to make sure that compositional simulator can predict the analytical solutions for hydraulically fractured system and to eliminate the effect of the grid size and grid distribution.…”

Well-Test Analysis Following a Closed-Fracture Acidizing Treatment

“…The finite-conductivity vertical-fracture model 13 was also used to interpret the buildup data. A finite-conductivity fracture is feasible because a fracture exists before acid reaches the formation and very long channels within the fracture are created as acid enters the fracture.…”