State of the Art in Characterization of Frac Stage Geometry and Conductivity Using Pressure Leakoff

2021 ◽  
Author(s):  
Mohamed Ibrahim Mohamed ◽  
Erdal Ozkan
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Transient Analysis ◽  
State Of The Art ◽  
Low Cost ◽  
Pressure Data ◽  
Pressure Transient Analysis ◽  
Fracture Conductivity ◽  
Pressure Transient ◽  
Half Length

Abstract Pressure-transient analysis (PTA) is widely used in the industry to estimate fracture half-length, height, and skin due to hydraulic fracturing as well as reservoir parameters. PTA studies focus on pressure data from long shut-in periods and diagnostic fracture injection tests (DFITs), while analyzing the pressure data recorded during the hydraulic fracture treatment has been overlooked. This paper details the state-of-the-art in applying pressure transient analysis to better estimate hydraulic fracture conductivity and dimensions and improve treatment designs stage by stage. The initial portion of this paper describes the application of a novel and low-cost diagnostic method for post-fracture analysis. The bulk of the paper is dedicated to present case histories that illustrate the PTA of the recorded pressure data during treatment to obtain estimates of fracture dimensions and conductivity. The pressure recorded during each stage is processed to ensure the proper data quality and the pressure falloff at the end of the stage is filtered out. The pressure is then analyzed for multi-cluster, finite-conductivity fractures, to obtain the fracture half-length, conductivity, and leakoff. Calculated parameters from each stage are compared to provide insights into the hydraulic fracture design and confirm the adequacy of the treatment design along the well. The results from stage leakoff pressure analysis are very valuable in confirming relative fracture conductivity and providing a qualitative measure of fracture length and height. The total stimulated reservoir area (SRA) calculated using the proposed method yields comparable values to SRA obtained from buildup analysis. The information provided is as valuable and comparable as that from direct near-wellbore diagnostics, such as radioactive traces, temperature logging, real-time micro-seismic monitoring, and production logging. The paper proposes a novel, low-cost analytical PTA method for estimating fracture dimensions, skin, and leakoff coefficient. We illustrate – with several field cases – that conventional post-fracture techniques can be integrated with the stage by stage PTA analysis to provide not only a more consistent and systematic analysis but also a more accurate assessment of treatment effectiveness. The findings of this paper help improve the efficiency of multistage hydraulic fracturing stimulation of horizontal wells.

Revision of Pressure Transient Analysis in Mature Condensate-Rich Tight Gas Fields in Sultanate of Oman

2022 ◽  
Author(s):  
Ahmed Elsayed Hegazy ◽  
Mohammed Rashdi
Keyword(s):  
Transient Analysis ◽  
Horizontal Wells ◽  
Development Planning ◽  
Reservoir Modeling ◽  
Sultanate Of Oman ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Full Field ◽  
Gas Fields ◽  
Half Length

Abstract Pressure transient analysis (PTA) has been used as one of the important reservoir surveillance tools for tight condensate-rich gas fields in Sultanate of Oman. The main objectives of PTA in those fields were to define the dynamic permeability of such tight formations, to define actual total Skin factors for such heavily fractured wells, and to assess impairment due to condensate banking around wellbores. After long production, more objectives became also necessary like assessing impairment due to poor clean-up of fractures placed in depleted layers, assessing newly proposed Massive fracturing strategy, assessing well-design and fracture strategies of newly drilled Horizontal wells, targeting the un-depleted tight layers, and impairment due to halite scaling. Therefore, the main objective of this paper is to address all the above complications to improve well and reservoir modeling for better development planning. In order to realize most of the above objectives, about 21 PTA acquisitions have been done in one of the mature gas fields in Oman, developed by more than 200 fractured wells, and on production for 25 years. In this study, an extensive PTA revision was done to address main issues of this field. Most of the actual fracture dynamic parameters (i.e. frac half-length, frac width, frac conductivity, etc.) have been estimated and compared with designed parameters. In addition, overall wells fracturing responses have been defined, categorized into strong and weak frac performances, proposing suitable interpretation and modeling workflow for each case. In this study, more reasonable permeability values have been estimated for individual layers, improving the dynamic modeling significantly. In addition, it is found that late hook-up of fractured wells leads to very poor fractures clean out in pressure-depleted layers, causing the weak frac performance. In addition, the actual frac parameters (i.e. frac-half-length) found to be much lower than designed/expected before implementation. This helped to improve well and fracturing design and implementation for next vertical and horizontal wells, improving their performances. All the observed PTA responses (fracturing, condensate-banking, Halite-scaling, wells interference) have been matched and proved using sophisticated single and sector numerical simulation models, which have been incorporated into full-field models, causing significant improvements in field production forecasts and field development planning (FDP).

Transient Pressure Analysis of Wells Intercepted by Partially Penetrating Finite Conductivity Hydraulic Fractures

2013 ◽  
Vol 446-447 ◽  
pp. 479-485
Author(s):  
De Tang Lu ◽  
Qing Xie ◽  
Cong Niu ◽  
Lei Wang
Keyword(s):  
Hydraulic Fracture ◽  
Transient Analysis ◽  
Contradictory Result ◽  
Hydraulic Fractures ◽  
Finite Conductivity ◽  
Well Test ◽  
Analysis Model ◽  
Transient Pressure ◽  
Pressure Transient Analysis ◽  
Pressure Transient

Most current pressure transient analysis techniques of hydraulically fractured wells are based on the fully penetrating assumption, which assumes equal thickness of hydraulic fracture and the formation. However, field application show that the fractures thickness can be shorter than the thickness of formation, which leads to vertical flow into the fracture. Thus applying the thickness equality assumption of current well test models to a partial penetrating fracture may give contradictory result. Further, there are very few studies concerning pressure transient analysis of partial penetrated wells. So it is important to develop analysis model and procedure to this type of fracture. In this paper, we presented an analytical model for partially penetrating hydraulic fracture in isotropic systems, along with the assumption that fracture is finite conductive. This model is then applied in the analysis of field production data, which verified validity of this new model.

Pressure-Transient Analysis of a Well With an Inclined Hydraulic Fracture

2010 ◽  
Vol 13 (06) ◽  
pp. 845-860 ◽  
Author(s):  
Anh V. Dinh ◽  
Djebbar Tiab
Keyword(s):  
Flow Regime ◽  
Hydraulic Fracture ◽  
Transient Analysis ◽  
Hydraulic Fractures ◽  
Pressure Derivative ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Fracture Models ◽  
Infinite Conductivity ◽  
Conductivity Models

Summary Hydraulic fracturing is an important well-stimulation technique that has been widely used in the oil and gas industry. Most of the pressure-transient-analysis techniques to analyze pressure responses of fractured wells are based on the assumption that the fracture is either vertical or horizontal. However, a hydraulic fracture could be inclined with a nonzero angle with respect to the vertical direction. Field studies have shown that most hydraulic fractures are not perfectly vertical. Thus, for an inclined hydraulic fracture, the vertical-orientation assumption may lead to erroneous results in welltest analysis, especially when the inclination angle is significant. However, there are very few studies concerning pressure-transient analysis of inclined hydraulic fractures, and there is no applicable well-test-analysis procedure available for inclined fractures. The purpose of this study is to develop a technique, on the basis of the pressure-derivative concept, for interpreting pressuretransient tests in wells with an inclined hydraulic fracture. Detailed analysis of unsteady-state pressure behavior of a fully penetrating inclined fracture in an infinite-slab reservoir was provided. Both uniform-flux and infinite-conductivity models were considered. The study has shown that inclined-fracture pressure data exhibit flow regimes similar to those for vertical fractures. Those flow regimes are linear and pseudoradial flow for both uniform-flux and infinite-conductivity models. However, for the infinite-conductivity model, a biradial- (or elliptical) flow regime is also observed. In the case of a high formation-thickness/fracture-half-length ratio and high angle of inclination, both uniform-flux and infiniteconductivity inclined-fracture models exhibit an additional flow regime, called early radial (ER) flow in this paper. This ER-flow regime for an inclined hydraulic fracture has not been mentioned in the literature before. A type-curve-matching technique was developed in this study using both pressure and pressure-derivative curves. This typecurve-matching procedure can be used to obtain the following parameters: fracture half-length, inclination angle, formation permeability, and the pseudoskin factor. The results should be verified with other pressure plots such as the semilog plot of vs. t and the Δp-vs.-t1/2 plot. A set of type curves with associated data was also provided for uniform-flux and infinite-conductivity inclined- fracture models. Detailed explanations, tables, figures, and a numerical example are included in this paper.

A Semianalytical Model for Pressure-Transient Analysis of Fractured Wells in Unconventional Plays With Arbitrarily Distributed Discrete Fractures

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2041-2059 ◽  
Author(s):  
Zhiming Chen ◽  
Xinwei Liao ◽  
Kamy Sepehrnoori ◽  
Wei Yu
Keyword(s):  
Fluid Flow ◽  
Hydraulic Fracture ◽  
Transient Analysis ◽  
Fractured Reservoirs ◽  
Naturally Fractured Reservoirs ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Fracture Networks ◽  
Pressure Transient Analysis ◽  
Pressure Transient

Summary In this paper, we present an efficient semianalytical model for pressure-transient analysis in fractured wells by considering arbitrarily distributed fracture networks. The semianalytical model included three domains: matrix, hydraulic-fracture networks, and discrete natural fractures. Using the line-source function, we developed the diffusivity equation for fluid flow in matrix. By applying the vertex-analysis technique, we eliminated the flow interplay at fracture intersections and established the diffusivity equations for fluid flow in hydraulic-fracture networks and isolated natural fractures. The pressure-transient solution of these diffusivity equations was obtained using Laplace transforms and the Stehfest numerical inversion. Results showed that with the discrete natural fractures, a “V-shaped” pressure derivative (the classical dual-porosity feature of naturally fractured reservoirs) emerged. With the hydraulic-fracture networks, the reservoir system would exhibit pressure behaviors such as “pseudoboundary-dominated flow,” “fracture-interference flow,” and “fluid-feed flow.” All these pressure characteristics were dependent on the properties and geometries of natural/hydraulic fractures. In addition, through synthetic field application, we found that different (natural/hydraulic) fracture distributions and geometries had distinct behaviors of pressure derivatives, which may provide an effective tool to identify the properties of randomly distributed natural fractures as well as complex hydraulic fractures in unconventional plays.

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