Early-Time Pressure Buildup Analysis for Prudhoe Bay Wells

1984 ◽  
Vol 36 (02) ◽  
pp. 311-319 ◽  
Author(s):  
R.M. McKinley ◽  
T.D. Streltsova
Keyword(s):  
Time Pressure ◽  
Early Time ◽  
Pressure Buildup ◽  
Prudhoe Bay

New Early Formation Pressure System Field Test Results and Advances in Early Time Pressure Buildup Analysis

1997 ◽  
Author(s):  
Neal G. Skinner ◽  
Mark A. Proett ◽  
Paul D. Ringgenberg ◽  
Wilson C. Chin ◽  
Reddy Aadireddy
Keyword(s):  
Field Test ◽  
Time Pressure ◽  
Early Time ◽  
Test Results ◽  
Formation Pressure ◽  
Pressure System ◽  
Pressure Buildup ◽  
Early Formation

Best Practices in DFIT Interpretation: Comparative Analysis of 62 DFITs from Nine Different Shale Plays

2022 ◽  
Author(s):  
Mark Mcclure ◽  
Garrett Fowler ◽  
Matteo Picone
Keyword(s):  
Pressure Drop ◽  
Pore Pressure ◽  
Time Pressure ◽  
Early Time ◽  
Horizontal Wells ◽  
Late Time ◽  
Fracture Length ◽  
Well Spacing ◽  
Net Pressure ◽  
The Difference

Abstract In URTeC-123-2019, a group of operators and service companies presented a step-by-step procedure for interpretation of diagnostic fracture injection tests (DFITs). The procedure has now been applied on a wide variety of data across North and South America. This paper statistically summarizes results from 62 of these DFITs, contributed by ten operators spanning nine different shale plays. URTeC-123-2019 made several novel claims, which are tested and validated in this paper. We find that: (1) a ‘compliance method’ closure signature is apparent in the significant majority of DFITs; (2) in horizontal wells, early time pressure drop due to near-wellbore/midfield tortuosity is substantial and varies greatly, from 500 to 6000+ psi; (3) in vertical wells, early-time pressure drop is far weaker; this supports the interpretation that early- time pressure drop in horizontal wells is caused by near-wellbore/midfield tortuosity from transverse fracture propagation; (4) the (not recommended) tangent method of estimating closure yields Shmin estimates that are 100-1000+ psi lower than the estimate from the (recommended) compliance method; the implied net pressure values are 2.5x higher on average and up to 5-6x higher; (5) as predicted by theory, the difference between the tangent and compliance stress and net pressure estimates increases in formations with greater difference between Shmin and pore pressure; (6) the h-function and G-function methods allow permeability to be estimated from truncated data that never reaches late-time impulse flow; comparison shows that they give results that are close to the permeability estimates from impulse linear flow; (7) false radial flow signatures occur in the significant majority of gas shale DFITs, and are rare in oil shale DFITs; (8) if false radial signatures are used to estimate permeability, they tend to overestimate permeability, often by 100x or more; (9) the holistic-method permeability correlation overestimates permeability by 10-1000x; (10) in tests that do not reach late-time impulse transients, it is reasonable to make an approximate pore pressure estimate by extrapolating the pressure from the peak in t*dP/dt using a scaling of t^(-1/2) in oil shales and t^(3/4) in gas shales. The findings have direct practical implications for operators. Accurate permeability estimates are needed for calculating effective fracture length and for optimizing well spacing and frac design. Accurate stress estimation is fundamental to hydraulic fracture design and other geomechanics applications.

INFLUENCE OF TIDAL PHENOMENA ON INTERPRETATION OF PRESSURE BUIILD-UP AND PULSE TESTS

1976 ◽  
Vol 16 (1) ◽  
pp. 99 ◽  
Author(s):  
A.K. Khurana
Keyword(s):  
Time Pressure ◽  
Pressure Gauge ◽  
Early Time ◽  
Late Time ◽  
Time Lags ◽  
Pressure Oscillations ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Gippsland Basin

Bottom-hole pressure tests conducted in the Kingfish oil reservoir (located in Gippsland Basin - Offshore Victoria) during 1974 and 1975 using a high sensitivity surface recording electronic bottom-hole pressure gauge indicated the presence of sinusoidal pressure oscillations in the reservor. The oscillations are of the order of 0.1 psi in amplitude and their frequency suggests that they are in some way related to tidal phenomena.Although the oscillations do not affect production, they do influence interpretation of pressure build-up and pulse tests. Interpretations of both late time pressure build-up behaviour and pulse tests of small response magnitude and long time lags are considered to be particularly susceptible to errors due to these oscillations if they are not recognized and corrected for. Interpretations of early time pressure build-up data and pulse tests of definite response and relatively short time lags are not regarded as being significantly affected.The physical mechanism causing these pressure oscillations in the reservoirs is not known. However, one of the various possible hypotheses is that the Latrobe Formation sands could be outcropping on the ocean floor at abyssal depths southeast of Kingfish and that the pressure transients generated by changes in the hydrostatic head due to surfate tides are transmitted hydraulically to the reservoir. If this hypothesis is proved to be valid it could influence pressure performance predictions of Gippsland Basin reservoirs.

Finite Horizontal Well in a Uniform-Thickness Reservoir Crossing a Natural Fracture Normally

SPE Journal ◽  
2013 ◽  
Vol 18 (05) ◽  
pp. 982-992 ◽  
Author(s):  
Michael Prats ◽  
R.. Raghavan
Keyword(s):  
Horizontal Well ◽  
Time Pressure ◽  
Finite Thickness ◽  
Early Time ◽  
Natural Fracture ◽  
Late Time ◽  
Arithmetic Average ◽  
Analytic Expressions ◽  
Accelerate Convergence ◽  
Instantaneous Source

Summary The instantaneous source solutions of Prats and Raghavan (2012) and the method of images are used to develop analytic expressions for the pressure distribution in a three-region composite reservoir of finite thickness produced by a finite-length horizontal well that is oriented perpindicular to the interfaces. The composite reservoir is assumed to be infinite in its lateral extents; the outer regions represent the reservoir, and the central region represents a thin natural fracture of relatively high permeability. In most of the cases considered, the well is completed in all three zones. The computational scheme is shown to be both viable and robust. The Shanks (1955) transformation is used to accelerate convergence. Pressure traces are logarithmic in time at early and late times for any well configuration examined here. Early-time pressure characteristics are similar to those discussed in Prats and Raghavan (2012). The duration of the early semilogarithmic responses is mediated not only by the presence of the higher-permeability natural fracture, as before, but also now by the interaction of the upper and lower boundaries with the well. Late-time semilogarithmic responses, however, are distinctly different. Their slope is inversely proportional to the product of the formation thickness and the arithmetic average permeability of the two regions that sandwich the fracture. This result holds even when the well does not cross the natural fracture. We expect this conclusion to apply to a composite system consisting of more than three regions. Observations concerning the late-time slope represent the central finding of this study. A relationship is given for the late-time performance of any horizontal well in terms of that of a vertical well with a constant pseudoskin. Pseudoskin equivalents are reported for all cases discussed.

Pressure Buildup Analysis of Prudhoe Bay Wells

1982 ◽  
Vol 34 (02) ◽  
pp. 387-396 ◽  
Author(s):  
Michael E. Brown ◽  
Ming-Lung Mao
Keyword(s):  
Pressure Buildup ◽  
Prudhoe Bay

Well Test Analysis for Wells Producing Layered Reservoirs With Crossflow

1985 ◽  
Vol 25 (03) ◽  
pp. 380-396 ◽  
Author(s):  
R. Prijambodo ◽  
R. Raghavan ◽  
A.C. Reynolds
Keyword(s):  
Single Layer ◽  
Early Time ◽  
Test Period ◽  
Transitional Period ◽  
Well Test ◽  
Layer System ◽  
Well Test Analysis ◽  
Test Analysis ◽  
Pressure Buildup ◽  
Short Time

Well Test Analysis for Wells Producing Layered Reservoirs Producing Layered Reservoirs With Crossflow Abstract The pressure response of a well producing a two-layer reservoir with crossflow is examined. Virtually all studieson the response of a well in multilayered systems with crossflow claim that after a few hours of production theses ystems behave as if they are single-layer systems. A careful examination of the early-time performance of a well in a reservoir with crossflow indicates that its behavior is remarkably different from that of an equivalent single-layer system and is influenced significantly by the degree of communication. It is important to understand short-time behavior, since the time span of virtually allpressure buildup tests encompasses the duration in which pressure buildup tests encompasses the duration in which a layered reservoir with crossflow may not behave as ifit were a single-layer system. Thus, interpretations of pressure buildup data based on single-layer theory can be pressure buildup data based on single-layer theory can be erroneous. In this study, we show that the flowing pressure response of a well at early times can be divided into threeflow periods. The first period is one in which the reservoir behaves as if it were a stratified (no-crossflow)system. This period is followed by a transitional period. The response of the well during this period depends onthe contrast in horizontal permeabilities and on the degreeof communication between the layers. During the third period, the reservoir can he described by an equivalent period, the reservoir can he described by an equivalent single-layer system. An examination of the time ranges of the various flowperiods indicates that, unless tests are designed periods indicates that, unless tests are designed properly, most of the interpretable pressure buildup data would properly, most of the interpretable pressure buildup data would be measured during the time the well response is influenced by the transitional period. The influence of the skin regions on the well responseis examined. The significance of the estimate of the skin factor obtained from a pressure test is discussed. We showthat the nature and the magnitude of the skin regions andthe size of the reservoir determine the applicability of conventional semilog procedures to systems with interlayer communication. Introduction The economic consequences of interlayer crossflow arewell established in the literature. Several studies have examined the well response in a reservoir with interlayer communication. However, most of these studies have been concerned primarily with the long-term performance of the well. A reservoir with crossflow can be representedby a single-layer reservoir of equal volume if the flow capacity of the single-layer system is equal to the arithmetic sum of the flow capacities of all layers. Some of these studies also have shown that the early-time response of a well draining a reservoir with interlayer crossflow is similar to the response of a well in a stratified(no-crossflow, commingled) reservoir. Undoubtedly, a transitional period must exist between these two extremes. None of the works cited previously discuss the duration of or the characteristics of the transitional period. If oneis interested in short-time testing, such as pressure builduptests, then it is imperative that the duration of the transitional period and the characteristics of the well responseduring this period be known. For example, if the duration of the test period is such that the well behaves as ifit drains a stratified system or a homogeneous system, then classical well test theories should be applicable. On the other hand, if the test period is such that the transitional period governs the well response, then important questions need to be answered. First, what are the magnitudes of the errors that would result if data during this period are analyzed by conventional procedures? Second, what are the parameters that control the duration of the transitional flow period? Third, is it possibleto obtain reservoir characteristics from a pressure buil duptest? None of the studies in the literature considers the influence of the skin regions on the well response. The skin regions have a significant influence on interlayer crossflow. In this study we show that the skin regions can havea dramatic influence on the well response, particularly during early times. We also show that conventional interpretations of flow behavior in the skin region are inadequate if the layers are in communication. The objective of this paper is to present a thorough examination of the performance of a well in a reservoir with intelayer crossflow. We intend to address the questions raised in the preceding paragraphs. The determination of formation parameters will be discussed. The results obtained here are applicable to both pressure transient testsand production logging. SPEJ P. 380

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