Application of catastrophe theory to fracability evaluation of deep shale reservoir
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ICCESEN 2017
Application of catastrophe theory to fracability evaluation of deep shale reservoir Wenbao Zhai 1 & Jun Li 1 & Yingcao Zhou 2 Received: 23 September 2018 / Accepted: 6 February 2019 # Saudi Society for Geosciences 2019
Abstract Fracability evaluation is one of the great challenges during the shale gas development, which has become a hotspot for the exploration of unconventional oil and gas. Although much research work was conducted and some evaluation models were developed, most of them could not be applied to practical engineering operations for deep shale gas development. In this paper, a multi-level sub-system was developed based on the analytic hierarchy process, and then, a catastrophe evaluation model, avoiding over-subjective in defining the weighting coefficient of factors, was proposed to evaluate deep shale reservoirs’ fracability by using the catastrophe theory. Finally, the model was verified by using engineering data in five deep shale gas wells. The analytic results showed that the calculated results of the catastrophe evaluation model are in good agreement with the facts compared with the analytic hierarchy process. Moreover, the general expression for the potential function and its normalization formula of the common catastrophe model with arbitrary dimensions could also be derived recursively to meet practical applications. Therefore, the catastrophe evaluation model was simple and suitable for the wide application, which provides new sights for the pre-fracturing prediction and post-fracturing evaluation during deep shale reservoirs development. Keywords Deep shale reservoir . Catastrophe theory . Analytic hierarchy process (AHP) . Weighting coefficient . Multi-level sub-system
Introduction Fracability evaluation, which is one of the great challenges during the shale gas development, is the foundation of multistage fracturing technology, especially deep shale gas development (buried depth > 3500 m) (Tang et al. 2012). For the hydraulic fracturing, selecting points, where the fracability is higher, is necessary (Meng et al. 2018; Peng and Li 2018; Zhao et al. 2018). In recent years, although numerous studies have been conducted on quantifying reservoir fracability by both scholars and corporations (Fang and Amro 2014; Jahandideh and This article is part of the Topical Collection on Geo-Resources-EarthEnvironmental Sciences * Jun Li [email protected] 1
College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing, China
2
CNPC Engineering Technology R&D Company Limited, Beijing, China
Jafarpour 2016; Jin et al. 2015), most related studies often have disadvantages in subjectivity and complexity associated with the weight determination procedure. It is well known that the indicators of the factor weights were usually aggregated into a composite indicator in the process of analysis, and this weight determination procedure was generally referred to as analytic hierarchy process (AHP) or fuzzy AHP (Sima et al. 2015; Sui et al. 2016). The indices aggregation pro
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