New Correlations of Acid-Fracture Conductivity at Low Closure Stress Based on the Spatial Distributions of Formation Properties

Mou, Jianye; Zhu, Ding; Hill, A.D.

doi:10.2118/131591-pa

Cited by 13 publications

(9 citation statements)

References 13 publications

(12 reference statements)

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“…However, acidizing will decreases hardness of fracture plane by 30%–70%, which makes the proppant embed into the rough closed fractures, reducing fracture conductivity. Mou et al , developed a 3D medium-scale model of acid fracturing and verified the simulation result with experiment of fracture conductivity in acid fracturing. It is thought that the conductivity of fracture is dependent on corrosion mode of fracture plane, which is also dependent on permeability and distribution of minerals, and the more rough fracture plane produces higher conductivity, which is due to deeper channel produced within the same acid residence time.…”

Section: Introductionmentioning

confidence: 90%

Evaluation of Acid Fracturing Treatments in Shale Formation

et al. 2017

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Hydraulic fracturing by stimulated reservoir volume (SRV) is a necessity to realize commercial development of shale gas, and its stimulation mechanism still needs further study, and the effectiveness of supplementary stimulation measures needs further exploration. The shale always contains some carbonate minerals. This paper tests the permeability of acid-etched fracture in shale to explore the influence of carbonate mineral content, acid fluid types and concentration, fracture plane roughness, proppant, and confining pressure on the acid-etched effects in shale, and uses CT scanning to conduct research on variation of microscopic pore-throat texture in shale before and after acid-etching. The test shows that the roughness of the fracture plane perpendicular to the bedding plane is higher than the roughness of that paralleled to the bedding plane, and the roughness in both fracture planes perpendicular to and paralleled to the bedding plane increases as the carbonate minerals content increases. In same group of shale samples, the permeability of self-propped fracture before and after acid-etching respectively is positively correlated with the fractal dimension of the fracture plane before and after acid-etching, and the variation of permeability of self-propped fracture before and after acid-etching is also positively correlated with the variation of fractal dimension of fracture plane before and after acid-etching, which is not shown in different groups of shale samples. When the content of carbonate minerals in shale is between 10% and 30%, the relation between optimum HCL concentration and carbonate mineral content is expressed as Y (OptimumHCLconcentration) = −0.5X (Carbonatemineralcontent) + 0.15. If the shale has a high carbonate mineral content (>30%), the effect of acid-etching is not easily controlled, so the technique of acid fracturing should be carried out cautiously. The permeability of single-layer proppant and self-propped fracture after acid-etching conforms to Walsh theory within certain pressure, and variation and migration of curve slope reflects unstable arrangement, imbedding, and crush of proppant, and nonreactive filled impurity of clay and quartz desquamated and migrated, which coincides well with constant variation of permeability. Applying proper acid fluids and optimum concentration in shale with varying carbonate contents will increase pore size, fracture width, and fracture number. For the shale with abundant calcite-cemented fractures, the optimum acid fluid concentration should be increased properly. Due to ultralow permeability of the matrix in shale, even high concentration acid fluid could not penetrate the core with barren natural fractures or calcium-filled fractures. The results of research provide valuable information for design of acid fracturing in shale play.

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Section: Introductionmentioning

confidence: 90%

Evaluation of Acid Fracturing Treatments in Shale Formation

et al. 2017

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“…More details on how the empirical acid-fracture correlations presented here were derived are given by Mou et al (2011), Deng et al (2011, Mou (2009), andDeng (2010). The correlations were derived by first determining the etching pattern created in hundreds of simulations of acid transport and dissolution through a portion of a fracture domain, and then calculating the resulting fracture conductivity at zero closure stress.…”

Section: Permeability-distribution-dominant Casesmentioning

confidence: 99%

“…On the basis of the spatial distributions of formation properties, Mou et al (2010bMou et al ( , 2011 have developed new correlations of acid-fracture conductivity at zero closure stress. Fracture surface-etching profiles control the conductivity at zero closure stress, while the conductivity change with closure stress is also a function of rock elastic properties.…”

Section: Introductionmentioning

confidence: 99%

A New Correlation of Acid-Fracture Conductivity Subject to Closure Stress

Deng

Mou

Hill

et al. 2012

SPE Production &Amp; Operations

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The conductivity of an acid-etched fracture depends strongly on void spaces and channels along the fracture resulting from uneven acid etching of the fracture walls. In this study, we modeled deformation of the rough fracture surfaces acidized in heterogeneous formations based on synthetic permeability distributions and developed a new correlation to calculate the acid-etched fracture conductivity.In our previous work, we modeled the dissolution of the fracture surfaces in formations having small-scale heterogeneities in permeability. The characterization of the correlated permeability fields of rock includes the average permeability, normalized correlation lengths in both horizontal and vertical directions, and normalized standard deviation. These statistical parameters have a significant influence on the fracture-etching profiles obtained from the model. Beginning with this fracture-width distribution, we have modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. The elastic properties of the rock, such as Young's modulus and Poisson's ratio, have effects on the size of the spaces remaining open after fracture closure. After the model yields the width profile under closure stress, the overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system.In this paper, we introduce our models and investigate the effects of permeability and mineralogy distributions and rock elastic properties on the overall conductivity of an acid-etched fracture. A new acid-fracture conductivity correlation is developed on the basis of many numerical experiments.

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“…A new correlation was proposed by Mou and Deng (Deng et al 2012), which takes into account the heterogeneous distribution of mineralogy and permeability in the rock, and the surface roughness, to calculate the acid fracture conductivity. First, an intermediate scale 3D acid fracturing model was developed by Mou et al (2010Mou et al ( , 2011, in which the calculation domain is 10 ft by 10 ft. Then, using the model, the effect of mineralogy, permeability, and surface roughness on the created conductivity under zero closure stress was examined. After that, the results of Mou's work were combined with the outcome of the study on the fracture closure and the conductivity decrease as a function of closure stress (Deng et al 2011).…”

Section: Acid Fracture Conductivity Correlationsmentioning

confidence: 99%

Development of Acid Fracturing Model for Naturally Fractured Reservoirs

Ugursal

Zhu

Hill

2019

SPE Production &Amp; Operations

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A successful application of the acid fracturing stimulation in naturally fractured carbonate reservoirs is challenged by an increased acid leakoff into natural fractures intersecting a hydraulically induced (main) fracture. This may limit the propagation of the main fracture resulting in conductivity reduction. At the same time, the etching of the natural fractures by the leakoff acid may increase the overall conductivity of the fracture system resulting in enhanced well productivity. The effect of the natural fractures on the efficiency of acid fracturing stimulation treatment is not fully understood. A model was developed to evaluate the acid fracturing performance in naturally fractured carbonate reservoirs.The model simulates an acid fracturing stimulation and production in a vertical well located in the center of a rectangular reservoir. The well contains a bi-wing vertical hydraulically induced fracture intersected by symmetric transverse natural fractures. The model simulates the acid flow

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New Correlations of Acid-Fracture Conductivity at Low Closure Stress Based on the Spatial Distributions of Formation Properties

Cited by 13 publications

References 13 publications

Evaluation of Acid Fracturing Treatments in Shale Formation

Evaluation of Acid Fracturing Treatments in Shale Formation

A New Correlation of Acid-Fracture Conductivity Subject to Closure Stress

Development of Acid Fracturing Model for Naturally Fractured Reservoirs

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