A Comprehensive Model for Estimating Stimulated Reservoir Volume Based on Flowback Data in Shale Gas Reservoirs

Qi Chen,Guoxuan Ren,Dan Zhu,Yuan Zhang,Jinghong Hu,Shaojun Wang

doi:10.1155/2020/8886988

Abstract

Stimulated reservoir volume (SRV) which is generated by horizontal drilling with multistage hydraulic fracturing governs the production in the shale gas reservoirs. Although microseismic data has been used to estimate the SRV, it is high-priced and sometimes overestimated. Additionally, the effect of stress sensitivity on SRV is not considered in abnormal overpressure areas. Thus, the objective of this work is to characterize subsurface fracture networks with stress sensitivity of permeability through the shale gas well production data of the early flowback stage. The flowback regions are first identified with the flowback data of two shale gas wells in South China. Then, we measured the permeability stress sensitivity of the core after fracturing, coupled to the dynamic relative permeability (DRP) calculation to obtain an accurate and simple DRP curve. After that, a comprehensive model is built considering dynamic two-phase relative permeability function and stress sensitivity. Finally, we compared the calculated results with the microseismic data. The results show that the proposed model could reasonably predict the SRV using the flowback data after fracturing. Additionally, compared with the microseismic data, the stress sensitivity should be included, especially in the abnormal overpressure block. It is believed that this mathematical model is accurate and useful. The work provides an efficient approach to estimate stimulated reservoir volume in the shale gas reservoirs.

Highlights

The development of shale gas has gained increasing attention with the decline of the production from conventional reservoirs [1, 2]
In order to facilitate the establishment of the mathematical model for the early gas production (EGP) phase, the fracture network around the shale gas fractured well is simplified into the Stimulated reservoir volume (SRV) region composed of the matrix system and fracture system
The following conclusions can be drawn: (1) The flowback data show that the gas-water ratio is Vshaped, i.e., the early descending stage and the late ascending stage in this field, which can be used to estimate the volume of the effective fracture system

Summary

Introduction

The development of shale gas has gained increasing attention with the decline of the production from conventional reservoirs [1, 2]. Due to the ultralow permeability of shales (from 10−23 to 10−17 m2) [3], a combination of horizontal drilling and multistage hydraulic fracturing has been widely used to SRV, which increases effective contact significantly to improve gas production from an individual well. Characterization of the stimulated reservoir volume appears to be of vital importance to manage and predict shale reservoir performance [4, 5]. While microseismic data has been extensively used to validate the stimulated reservoir volume, the SRV obtained directly from the microseismic data is generally overestimated. Implementation of microseismic techniques in a field sometimes is not cost-effective, which limits a wide application in fields

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Methods

Conclusion