Elliptical Flow Equations for Vertically Fractured Gas Wells

Hale, Brent W.; Evers, J.F.

doi:10.2118/8943-pa

Cited by 30 publications

(6 citation statements)

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“…We found that actual production data shows long-term linear flow for months and years in a large number of wells [2][3][4][5][6][7][8][9] because of the extremely low permeability in the reservoir.…”

Section: Introductionmentioning

confidence: 91%

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Transient Analysis of Tight Gas Well Performance – More Case Histories

Arevalo-Villagran

Cinco-Ley

Wattenbarger

et al. 2003

SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractProduction data from some gas fields show the presence of long-term linear flow for several years in a large number of wells, caused by the extremely low permeability in the reservoir. Long-term linear flow production may be generated and controlled in some cases by the reservoir geometry; in others it is controlled by the natural occurring reservoir properties. In this paper three physical scenarios that cause and control long-term linear flow in tight gas reservoirs are described. First, we analyze how parallel natural fractures lead to permeability anisotropy which causes long-term linear flow. An analytical matrix-parallel fracture model is presented. Second, we show how a fractured well in a tight gas reservoir causes linear flow perpendicular to the fracture. We focus on decline curve analysis methods for long-term linear flow in fractured tight gas wells. Third, we discuss long-term vertical linear flow in a high permeability streak in tight gas reservoirs. An analytical model to analyze long-term linear flow in a high permeability layer and 2D simulation results are shown. Formulas to estimate reservoir properties for both fractured tight gas wells with linear flow and vertical linear flow in a high permeability streak are shown. These formulas were developed for both infinite acting and closed reservoirs, under either constant bottomhole flowing pressure or constant gas rate conditions. A linear analysis can be applied to detect where the outer boundary effect occurs, by finding the slope of a [m(p i )-m(p wf )]/q g vs. t 1/2 plot. Values of k 1/2 A c , drainage area, and OGIP can be estimated without knowing prior porosity, permeability, and thickness. Application of this linear analysis to production analysis for conventional and tight gas wells and validation of the results by using numerical simulations are shown.

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Section: Introductionmentioning

confidence: 91%

“…Values of k = 1.2 md, s = -5. 9, and x f = 192 ft were estimated with a specialized plot of ∆m(p)/q g vs. log(t) using h net = 20 ft as the perforated interval.…”

Section: Production Analysis Of Well Datamentioning

confidence: 99%

Transient Analysis of Tight Gas Well Performance – More Case Histories

Arevalo-Villagran

Cinco-Ley

Wattenbarger

et al. 2003

SPE Annual Technical Conference and Exhibition

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“…This flow regime is characterized by parallel flow lines perpendicular to the hydraulic fracture (Arevalo-Villagran et al 2001). Many authors reported that this flow regime could extend for long period (Ammer 1984;Boardman and Knutson 1981;Hale 1986;Hale and Evers 1981;Nott and Hara 1991;Stright and Gordon 1983;Wattenbarger et al 1998). This flow regime occurs when the high conductivity fracture is created near the reservoir formation (Ramey 1970).…”

Section: Linear Flow Regimementioning

confidence: 99%

Incremental and acceleration production estimation and their effect on optimization of well infill locations in tight gas reservoirs

Dheyauldeen

Al-Fatlawi

Hossain

2021

J Petrol Explor Prod Technol

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The main role of infill drilling is either adding incremental reserves to the already existing one by intersecting newly undrained (virgin) regions or accelerating the production from currently depleted areas. Accelerating reserves from increasing drainage in tight formations can be beneficial considering the time value of money and the cost of additional wells. However, the maximum benefit can be realized when infill wells produce mostly incremental recoveries (recoveries from virgin formations). Therefore, the prediction of incremental and accelerated recovery is crucial in field development planning as it helps in the optimization of infill wells with the assurance of long-term economic sustainability of the project. Several approaches are presented in literatures to determine incremental and acceleration recovery and areas for infill drilling. However, the majority of these methods require huge and expensive data; and very time-consuming simulation studies. In this study, two qualitative techniques are proposed for the estimation of incremental and accelerated recovery based upon readily available production data. In the first technique, acceleration and incremental recovery, and thus infill drilling, are predicted from the trend of the cumulative production (Gp) versus square root time function. This approach is more applicable for tight formations considering the long period of transient linear flow. The second technique is based on multi-well Blasingame type curves analysis. This technique appears to best be applied when the production of parent wells reaches the boundary dominated flow (BDF) region before the production start of the successive infill wells. These techniques are important in field development planning as the flow regimes in tight formations change gradually from transient flow (early times) to BDF (late times) as the production continues. Despite different approaches/methods, the field case studies demonstrate that the accurate framework for strategic well planning including prediction of optimum well location is very critical, especially for the realization of the commercial benefit (i.e., increasing and accelerating of reserve or assets) from infilled drilling campaign. Also, the proposed framework and findings of this study provide new insight into infilled drilling campaigns including the importance of better evaluation of infill drilling performance in tight formations, which eventually assist on informed decisions process regarding future development plans.

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“…Estimate k from the slope (m) of the straight line using Eq. 11, and x f from the x-axis intercept (i) using Eq. 12.…”

Section: Elliptical Flow-based Pressure Transient Interpretation Techmentioning

confidence: 99%

A New Approach for Reliable Estimation of Hydraulic Fracture Properties in Tight Gas Wells

2007

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractGas wells in low-permeability formations usually require hydraulic fracturing to be commercially viable. Pressure transient analysis in hydraulically fractured tight gas wells is commonly based on analysis of three flow regimes: bilinear, linear and pseudo-radial. With current well test analysis techniques, a reliable estimation of hydraulic fracture and reservoir properties relies on occurrence of all these three flow regimes. Without the presence of pseudo-radial flow, neither reservoir permeability nor fracture half length can be independently estimated. In other words, to reliably estimate fracture half length, reservoir permeability has to be known. Since pseudo-radial flow is often absent, the estimation is uncertain and unreliable. On the other hand, elliptical flow, which exists between linear flow and pseudo-radial flow, is of long duration (typically months to years). We can acquire much rate and pressure data during this flow regime but no practical well test analysis technique is currently available to interpret these data. This paper presents a new approach to reliably estimate reservoir and hydraulic fracture properties from analysis of constant-rate drawdown pressure data obtained during the elliptical flow period. The method is based on equations modeling the elliptical flow regime and is applicable to estimate effective fracture half length, formation permeability and skin factor independently for both infinite-and finiteconductivity fractures. The method is iterative and features rapid convergence. It can estimate formation permeability when pseudo-radial flow does not exist. It can also be coupled with stable deconvolution technology, which convert variable production-rate and pressure measurements into an equivalent constant-rate pressure drawdown test, and thus provide property estimates from readily available, noisy production data. We present synthetic and field examples to illustrate the procedures and demonstrate the validity and applicability of the proposed approach.

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Elliptical Flow Equations for Vertically Fractured Gas Wells

Cited by 30 publications

References 0 publications

Transient Analysis of Tight Gas Well Performance – More Case Histories

Transient Analysis of Tight Gas Well Performance – More Case Histories

Incremental and acceleration production estimation and their effect on optimization of well infill locations in tight gas reservoirs

A New Approach for Reliable Estimation of Hydraulic Fracture Properties in Tight Gas Wells

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