Dynamic Integration of DTS Data for Hydraulically Fractured Reservoir Characterization with the Ensemble Kalman Filter

2014 ◽  
Author(s):  
M.. Tarrahi ◽  
E.. Gildin ◽  
J.. Moreno ◽  
S.. Gonzales
Keyword(s):  
Kalman Filter ◽  
Real Time ◽  
Hydraulic Fracture ◽  
Ensemble Kalman Filter ◽  
Monitoring Data ◽  
Hydraulic Fractures ◽  
Fracture Characterization ◽  
Fracture Conductivity ◽  
Fracture Characteristics ◽  
Fracturing Process

Abstract The deployment of fiber-optic-based distributed temperature sensing (DTS) in hydraulically fractured wells has enabled us to observe the dynamic temperature profile along the wellbore during treatment, flow back and production not only as a postprocessing step but also in real-time monitoring applications of the hydraulic fracturing process. Fracture initiation points, vertical coverage and number of created fractures can be identified by DTS data. However, to evaluate the well performance, optimize future treatments and better understand fracture modeling, additional accurate quantitative information such as fracture conductivity and geometries need to be inferred from DTS data. In this study, we propose to set up a stochastic inverse problem to infer hydraulic fracture characteristics such as fracture conductivity and geometries by integrating real-time DTS monitoring data. We develop a synthetic non-isothermal simulation model containing a horizontal well with multi-stage transverse hydraulic fractures amenable for realist real-time DTS data. We also provide a comprehensive understanding of the effectiveness of different fracture and reservoir parameters in the monitored temperature data by means of sensitivity analysis. To estimate the hydraulic fracture characteristics, we employ the ensemble Kalman filter (EnKF), an ensemble based sequential model updating method, to assimilate DTS data. The EnKF enables us to perform quantitative fracture characterization and automatic history matching. The EnKF also offers several advantages for this application, including the ensemble formulation for uncertainty assessment, convenient gradient-free implementation, and the flexibility to incorporate additional monitoring data types. Examples are presented to illustrate the suitability of the EnKF-based fracture characterization for the inversion of DTS data to infer fracture geometries and conductivity. We demonstrate that by means of the EnKF we can identify accurately fracture halflength and fracture permeability from temperature inversion.

scholarly journals Numerical simulation on the simultaneous stress interference of parallel multiple hydraulic fractures

2021 ◽  
pp. 014459872110019
Author(s):  
Weiyong Lu ◽  
Changchun He
Keyword(s):  
Principal Stress ◽  
Hydraulic Fracture ◽  
Stress Ratio ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Fracture Spacing ◽  
Induced Stress ◽  
Minimum Principal Stress ◽  
Fracturing Process ◽  
Stress Ratios

During horizontal well staged fracturing, there is stress interference between multiple transverse fractures in the same perforation cluster. Theoretical analysis and numerical calculation methods are applied in this study. We analysed the mechanism of induced stress interference in a single fracture under different fracture spacings and principal stress ratios. We also investigated the hydraulic fracture morphology and synchronous expansion process under different fracture spacings and principal stress ratios. The results show that the essence of induced stress is the stress increment in the area around the hydraulic fracture. Induced stress had a dual role in the fracturing process. It created favourable ground stress conditions for the diversion of hydraulic fractures and the formation of complex fracture network systems, inhibited fracture expansion in local areas, stopped hydraulic fractures, and prevented the formation of effective fractures. The curves of the maximum principal stress, minimum principal stress, and induced principal stress difference with distance under different fracture lengths, different fracture spacings, and different principal stress ratios were consistent overall. With a small fracture spacing and a small principal stress ratio, intermediate hydraulic fractures were difficult to initiate or arrest soon after initiation, fractures did not expand easily, and the expansion speed of lateral hydraulic fractures was fast. Moreover, with a smaller fracture spacing and a smaller principal stress ratio, hydraulic fractures were more prone to steering, and even new fractures were produced in the minimum principal stress direction, which was beneficial to the fracture network communication in the reservoir. When the local stress and fracture spacing were appropriate, the intermediate fracture could expand normally, which could effectively increase the reservoir permeability.

scholarly journals Production Decline Analysis and Hydraulic Fracture Network Interpretation Method for Shale Gas with Consideration of Fracturing Fluid Flowback Data

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jianfeng Xiao ◽  
Xianzhe Ke ◽  
Hongxuan Wu
Keyword(s):  
Shale Gas ◽  
Hydraulic Fracture ◽  
Early Time ◽  
Fracture Network ◽  
Microseismic Monitoring ◽  
Monitoring Data ◽  
Fracturing Fluid ◽  
Fracture Conductivity ◽  
Fracture Length ◽  
Interpretation Method

After multistage hydraulic fracturing of shale gas reservoir, a complex fracture network is formed near the horizontal wellbore. In postfracturing flowback and early-time production period, gas and water two-phase flow usually occurs in the hydraulic fracture due to the retention of a large amount of fracturing fluid in the fracture. In order to accurately interpret the key parameters of hydraulic fracture network, it is necessary to establish a production decline analysis method considering fracturing fluid flowback in shale gas reservoirs. On this basis, an uncertain fracture network model was established by integrating geological, fracturing treatment, flowback, and early-time production data. By identifying typical flow-regimes and correcting the fracture network model with history matching, a set of production decline analysis and fracture network interpretation method with consideration of fracturing fluid flowback in shale gas reservoir was formed. Derived from the case analysis of a typical fractured horizontal well in shale gas reservoirs, the interpretation results show that the total length of hydraulic fractures is 4887.6 m, the average half-length of hydraulic fracture in each stage is 93.4 m, the average fracture conductivity is 69.7 mD·m, the stimulated reservoir volume (SRV) is 418 × 10 4   m 3 , and the permeability of SRV is 5.2 × 10 − 4   mD . Compared with the interpretation results from microseismic monitoring data, the effective hydraulic fracture length obtained by integrated fracture network interpretation method proposed in this paper is 59% of that obtained from the microseismic monitoring data, and the effective SRV is 83% of that from the microseismic monitoring data. The results show that the fracture length is smaller and the fracture conductivity is larger without considering the influence of fracturing fluid.

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