Estimation of fracture volume and its surface area on stimulated shale gas wells by material balance method
Received date: 2017-04-05
Revised date: 2017-06-15
Online published: 2017-07-10
The flowback data of stimulated shale gas wellusually show different features along with well production process，and consequently the data may be divided into two stages: the early gas production stage (EGP) and late gas production stage (LGP) according to the changes ofgas water ratio(GWR).The early stage indicates a two-phase flow，and the water phase is the dominant because the gas supply of shale matrix to the fracture network is still insufficient.Also，in this stage，the whole fracture network (including primary fractures，secondary fractures and connected natural fractures) can be regarded as a closed system.This paper established a material balance model to estimate the stimulated fracture volume and surface area via the early stage flowback data，and the validity of this model was verified through two field cases of Longmaxi Formation shale gas wells.The results showed that fracture volume of the analyzed wells was about 70% of the total injected fluid volume，and the fracture surface area reached 107m2.Huge fracture surface area indicatedthat complex fracture network had beenformed during fracturing，which couldsignificantly increase the drainage area of the stimulated wells.The analyticalresults of this model agreed well with the flowback data and well production characteristics.It further demonstratesthat this approach is an effective method to evaluate the fracture parameters of stimulated wells，and is of significance to field evaluation of fractured shale gas wells.
Key words： Shale gas; Flowback stages; Material balance; Fracture volume; Fracture surface area
Yang Bin，You Li-jun，Kang Yi-li，He Zhi-jun，Li Xiang-chen . Estimation of fracture volume and its surface area on stimulated shale gas wells by material balance method[J]. Natural Gas Geoscience, 2017 , 28(7) : 1059 -1064 . DOI: 10.11764/j.issn.1672-1926.2017.06.015
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