A Multi-Disciplinary Approach for Well Spacing and Treatment Design Optimization in the Midland Basin Using Lateral Pore Pressure Estimation and Depletion Modeling

2021 ◽  
Author(s):  
Taylor Levon ◽  
Kit Clemons ◽  
Ben Zapp ◽  
Tim Foltz
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Initial Study ◽  
Midland Basin ◽  
Well Spacing ◽  
Fracture Modeling ◽  
Original Target ◽  
Treatment Responses ◽  
Treatment Designs

Abstract With a recent trend in increased infill well development in the Midland basin and other unconventional plays, it has been shown that depletion has a significant impact on hydraulic fracture propagation. This is largely because production drawdown causes in-situ stress changes, resulting in asymmetric fracture growth toward the depleted regions. In turn, this can have a negative impact on production capacity. For the initial part of this study, an infill child well was drilled and completed adjacent to a parent well that had been producing for two years. Due to drilling difficulties, the child well was steered to a new target zone located 125 feet above the original target. However, relative to the original target, treatment data from the new zone indicated abnormal treatment responses leading to a study to evaluate the source of these variations and subsequent mitigation. The initial study was conducted using a pore pressure estimation derived from drill bit geomechanics data to investigate depletion effects on the infill child well. The pore pressure results were compared to the child well treatment responses and bottom hole pressure measurements in the parent well. Following the initial study, additional hydraulic fracture modeling studies were conducted on a separate pad to investigate depletion around the infill wells, determine optimal well spacing for future wells given the level of depletion, and optimize treatment designs for future wells in similar depletion scenarios. A depletion model workflow was implemented based on integrating hydraulic fracture modeling and reservoir analytics for future infill pad development. The geomechanical properties were calibrated by DFIT results and pressure matching of the parent well treatments for the in-situ virgin conditions. Parent well fracture geometries were used in an RTA for an analytical approach of estimating drainage area of the parent wells. These were then applied to a depletion profile in the hydraulic fracture model for well spacing analysis and treatment design sensitivities. Results of the initial study indicated that stages in the new, higher interval had higher breakdown pressures than the lower interval. Additionally, the child well drilled in the lower interval had normal breakdown pressures in line with the parent well treatments. This suggests that treatment differences in the wells were ultimately due to depletion of the offset parent well. Based on the modeling efforts, optimal infill well spacing was determined based on the on-production time of the parent wells. The optimal treatment designs were also determined under the same conditions to minimize offset frac hits and unnecessary completion costs. This case study presents the use of a multi-disciplinary approach for well spacing and treatment optimization. The integration of a novel method of estimating pore pressure and depletion modeling workflows were used in an inventive way to understand depletion effects on future development.

Impact of Geomechanics on Well Completion and Asset Development in the Bakken Formation

2015 ◽  
Author(s):  
Sameer Ganpule ◽  
Karthik Srinivasan ◽  
Tyler Izykowski ◽  
Barbara Luneau ◽  
Ernest Gomez
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Normal Pressure ◽  
In Situ Stress ◽  
Stress Profile ◽  
Well Spacing ◽  
Pressure Profiles ◽  
Asset Development ◽  
Pressure Regime

Abstract In-situ stress variability within a reservoir is a primary parameter that controls hydraulic fracture initiation, growth, connectivity, and ultimately drainage and well spacing. This paper highlights the importance of characterizing the variability of in-situ stress and demonstrates the risk of underestimating stimulation treatment size when a treatment design is applied in a “copy-paste” fashion without any modifications to account for variation in pore pressure and in-situ stress across a basin. Thermal maturity and hydrocarbon generation from unconventional shales has a direct effect on pore pressure and the in-situ stress distribution in reservoir and barrier rocks. An examination of the Bakken Petroleum System (BPS) identifies regions of thermal maturity and higher pore pressure due to hydrocarbon expulsion. Consequently, the elevated pore pressure and the resulting in-situ stress vary vertically and laterally within the basin. Multiple pore pressure profiles and corresponding stress profiles across the BPS were considered to quantify the impact of in-situ stress variability on hydraulic fracture geometry. These profiles include effects of normal pore pressure regime, over-pressure regime or pressure profiles transitioning from over pressure to normal pressure regimes. For a given stress profile, hydraulic fracture geometries are estimated using a fracture simulator, with multiple calibration points. The hydraulic fracture system and reservoir interactions are simulated in a subsequent production modeling phase which estimates drainage area characteristics, recovery forecasts and optimum well spacing for developing an asset. Results from stress profile sensitivity emphasize the need to address variability of in-situ stress as it directly impacts well spacing considerations in an asset development plan. For example, stress profile with a normal pore pressure regime results in longer hydraulic fracture lengths in the Middle Bakken (MB) thus requiring three wells per section to infill the asset. Conversely, stress profile with over-pressure regime in MB results in much shorter hydraulic fracture lengths thus requiring more than three wells per section to develop the asset. Incorrectly assuming overpressure in a normally pressured zone could lead to over-engineering of wells and unnecessary costs, whereas incorrectly assuming normal pressure in zones that are in fact overpressured could lead to sub-optimal completions and/or a reduction in overall production.

scholarly journals Laboratory Investigation on the -Effect of In-Situ Stresses on Hydraulic Fracture Containment

1982 ◽  
Vol 22 (03) ◽  
pp. 333-340 ◽  
Author(s):  
Norman R. Warpinski ◽  
James A. Clark ◽  
Richard A. Schmidt ◽  
Clarence W. Huddle
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Laboratory Experiments ◽  
In Situ Stress ◽  
Enhanced Production ◽  
In Situ Stresses ◽  
Extensive Growth ◽  
Stress Variations ◽  
Fracture Growth

Abstract Laboratory experiments have been conducted to determine the effect of in-situ stress variations on hydraulic fracture containment. Fractures were initiated in layered rock samples with prescribed stress variations, and fracture growth characteristics were determined as a function of stress levels. Stress contrasts of 300 to 400 psi (2 to 3 MPa) were found sufficient to restrict fracture growth in laboratory samples of Nevada tuff and Tennessee and Nugget sandstones. The required stress level was found not to depend on mechanical rock properties. However, permeability and the resultant pore pressure effects were important. Tests conducted at biomaterial interfaces between Nugget and Tennessee sandstones show that the resultant stresses set up near the interface because of the applied overburden stress affect the fracture behavior in the same way as the applied confining stresses. These results provide a guideline for determining the in-situ stress contrast necessary to contain a fracture in a field treatment. Introduction An under-standing of the factors that influence and control hydraulic fracture containment is important for the successful use of hydraulic fracturing technology in the enhanced production of natural gas from tight reservoirs. Optimally, this understanding would provide improved fracture design criteria to maximize fracture surface area in contact with the reservoir with respect to volume injected and other treatment parameters. In formations with a positive containment condition (i.e., where fracturing out of zone is not anticipated), long penetrating fractures could be used effectively to develop the resource. For the opposite case, the options would beto use a small treatment so that large volumes are not wasted in out-of-zone fracturing and to accept a lower productivity improvement, orto reject the zone as uneconomical. These decisions cannot be made satisfactorily unless criteria for vertical fracture propagation are developed and techniques for readily measuring the important parameters are available. Currently, both theoretical and experimental efforts are being pursued to determine the important parameters and their relative effects on fracture growth. Two modes of fracture containment are possible. One is the situation where fracture growth is terminated at a discrete interface. Examples of this include laboratory experiments showing fracture termination at weak or unbonded interfaces and theoretical models that predict that fracture growth will terminate at a material property interface. The other mode may occur when the fracture propagates into the bounding layer, but extensive growth does not take place and the fracture thus is restricted. An example is the propagation of the fracture into a region with an adverse stress gradient so that continued propagation results in higher stresses on the fracture, which limits growth, as suggested by Simonson et al. and as seen in mineback experiments. Another example is the possible restriction caused by propagation into a higher modulus region where the decreased width results in increased pressure drop in the fracture, which might inhibit extensive growth into that region relative to the lower modulus region. Other parameters, such as natural fractures, treatment parameters, pore pressure, etc., may affect either of these modes. Laboratory and mineback experiments have shown that weak interfaces and in-situ stress differences are the most likely factors to contain the fracture, and weak interfaces are probably effective only at shallow depths. Thus, our experiments are being performed to determine the effect of in-situ stresses on fracture containment, both in a uniform rock sample and at material properly interfaces. SPEJ P. 333^

scholarly journals The Effect of Hydraulic Fracture Geometry on Well Productivity in Shale Oil Plays with High Pore Pressure

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7727
Author(s):  
Daniela A. Arias Ortiz ◽  
Lukasz Klimkowski ◽  
Thomas Finkbeiner ◽  
Tadeusz W. Patzek
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Hydraulic Fractures ◽  
Shale Oil ◽  
Production Forecast ◽  
Fracture Geometry ◽  
Hydrocarbon Production ◽  
Reservoir Simulations ◽  
Bedding Planes

We propose three idealized hydraulic fracture geometries (“fracture scenarios”) likely to occur in shale oil reservoirs characterized by high pore pressure and low differential in situ stresses. We integrate these geometries into a commercial reservoir simulator (CMG-IMEX) and examine their effect on reservoir fluids production. Our first, reference fracture scenario includes only vertical, planar hydraulic fractures. The second scenario has stimulated vertical natural fractures oriented perpendicularly to the vertical hydraulic fractures. The third fracture scenario has stimulated horizontal bedding planes intersecting the vertical hydraulic fractures. This last scenario may occur in mudrock plays characterized by high pore pressure and transitional strike-slip to reverse faulting stress regimes. We demonstrate that the vertical and planar fractures are an oversimplification of the hydraulic fracture geometry in anisotropic shale plays. They fail to represent the stimulated volume geometric complexity in the reservoir simulations and may confuse hydrocarbon production forecast. We also show that stimulating mechanically weak bedding planes harms hydrocarbon production, while stimulated natural fractures may enhance initial production. Our findings reveal that stimulated horizontal bedding planes might decrease the cumulative hydrocarbon production by as much as 20%, and the initial hydrocarbon production by about 50% compared with the reference scenario. We present unique reservoir simulations that enable practical assessment of the impact of varied hydraulic fracture configurations on hydrocarbon production and highlight the importance of constraining present-day in situ stress state and pore pressure conditions to obtain a realistic hydrocarbon production forecast.

Estimation of hydraulic fracture pressure in clay

1994 ◽  
Vol 31 (6) ◽  
pp. 817-828 ◽  
Author(s):  
Knut H. Andersen ◽  
Colin G. Rawlings ◽  
Tom A. Lunne ◽  
Trond H. By
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Rational Approach ◽  
Laboratory Model ◽  
Drilling Mud ◽  
Stress Strain ◽  
Fracture Pressure ◽  
Fracture Tests ◽  
Mud Pressure

For offshore drilling, and in particular when drilling from fixed platforms in deep waters, the mud pressure will be high compared with the hydraulic fracture pressure (i.e., the formation strength) close to the sea floor. The first casing (the conductor) should therefore be installed to a depth where the formation strength is sufficient to prevent hydraulic fracturing of the soil. The consequences of hydraulic fracture could be mud flowing into the formation and loss of mud circulation. This slows down the drilling and, in cases where large quantities of mud flow into the formations beneath the platform, may even threaten the integrity of the foundation soils and create a safety problem. A conservative approach with too deep conductor setting depths will, on the other hand, lead to high unnecessary costs. This paper presents a new approach for calculating hydraulic fracture pressures. The new calculation approach considers two important factors that are generally not covered by theories found in the literature: nonlinearity of the stress–strain properties of the soil, and pore-pressure changes in the soil due to changes in total normal stress and shearing of the soil. The stress–strain properties and the shear-induced pore pressure are determined from laboratory tests. The proposed calculation approach has been verified against a series of laboratory model hydraulic fracture tests and in situ hydraulic fracture tests carried out at numerous offshore sites. The paper also presents a rational approach to establish the maximum allowable drilling mud pressure in clay formations and recommends partial safety coefficients that depend upon the consequences of hydraulic fracture and the quality of the soil data. Key words : hydraulic fracture, boreholes, clay, conductor setting depth, model tests, in situ tests, calculations.

The Conversion of Methyl-2-Acetoxyethyl-2′-Chloroethylamine to an Acetylcholine-Like Aziridinium Ion and its Action on the Isolated Guinea Pig Ileum

1972 ◽  
Vol 50 (8) ◽  
pp. 798-808 ◽  
Author(s):  
M. Hirst ◽  
C. H. Jackson
Keyword(s):  
Aqueous Solution ◽  
Guinea Pig ◽  
Muscle Tone ◽  
Recovery Period ◽  
Induced Responses ◽  
Agonist Activity ◽  
Guinea Pig Ileum ◽  
Aziridinium Ion ◽  
Treatment Responses

Methyl-2-acetoxyethyl-2′-chloroethylamine (acetyicholine-mustard) isomerizes in aqueous solution to form a cyclic ion, N-methyl-N-(2-acetoxyethyl)aziridinium, which structurally resembles acetylcholine. It is a potent stimulant of the guinea pig ileum, being approximately one-sixth as potent as acetylcholine at pH 7.4 and one-third as potent at pH 8.4. The agonist activity is inhibited by atropine, by preincubation with acetylcholinesterase, and pretreatment with thiosulfate ion. Mepyramine does not inhibit the stimulant action.One hour exposures of ileum segments to concentrations of acetylcholine-mustard in excess of those producing maximal responses, followed by a 1 h recovery period, did not produce evidence of postsynaptic receptor alkylation. Post-treatment responses to acetylcholine were slightly depressed, but these reductions were not related to the incubation concentrations of the agonist haloalkylamine. Pilocarpine-induced responses were unaltered by this treatment whereas 5-hydroxytryptamine responses were slightly potentiated and histamine responses were slightly and inconsistently modified.These treatments produced persistent, dose-related increases in muscle tone, an effect consistent with accumulations of spontaneously liberated acetylcholine and possibly caused by inhibition of in situ acetylcholinesterase.Ostensibly, the evidence suggests that the acetylcholine-like aziridinium ion can stimulate, but not inhibit, the muscarinic receptors of the guinea pig ileum.

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