Research on sensitivity damage of naturally fractured carbonate reservoirs in Ordos Basin
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ICCESEN 2017
Research on sensitivity damage of naturally fractured carbonate reservoirs in Ordos Basin Lufeng Zhang 1,2 & Fujian Zhou 1,2 & Jianye Mou 2 & Jin Wang 1,2 & Jie Wang 1,2 & Shicheng Zhang 1,2 Received: 7 November 2018 / Accepted: 5 September 2019 # Saudi Society for Geosciences 2019
Abstract Understanding mechanisms and performance of formation sensitivity damage in naturally fractured carbonate reservoirs is crucial for avoiding productivity attenuation at any development stage. In this paper, based on the investigation of reservoir microscopic feature, a series of experiments were conducted to systematically evaluate formation sensitivity damage through a multistep coreflood platform. Firstly, the influence of flow velocity on core permeability was studied. Then, coreflood experiments under the condition of beneath the threshold velocity were performed to research the influence of the salinity and PH value for the injected water on core permeability. Finally, four types of cores from Ordos Basin—matrix cores, non-packed cores, semipacked cores, and fully-packed cores—were used to conduct stress sensitivity damage experiments. Permeability is measured in the process of increasing confining pressure with a constant pore pressure. The experiment results show that the velocity sensitivity of the reservoir is medium to strong and the threshold velocity is 0.28 m/d. The water sensitivity is weak and the average water sensitivity index is 22.62%. There is no alkali sensitivity. The stress sensibilities of these four types of cores ranking from strong to weak are non-packed cores, semi-packed cores, packed cores, and matrix cores. With the decrease in packing degree of core fractures, the stress sensitivity of core permeability increases and the recovery degree of permeability decreases. The influence factors of sensitivity damage are systematically studied and it provides the suggestions for stimulation design and development of naturally fractured carbonate reservoirs in Ordos Basin. Keywords Fractured carbonate reservoir . Velocity sensitivity . Water sensitivity . Alkali sensitivity . Stress sensitivity
Introduction Based on the definition proposed by Yang and Civan F, Johnston et al., reservoir sensitivity damage is a generic term that rocks may suffer a sharp decrease in permeability when subjected to changes of reservoir conditions, which are inevitable during development (Yang 2011; Civan 2007). It is an undesirable operational and economic problem that can occur during the process of drilling, hydraulic fracturing, and This article is part of the Topical Collection on Geo-Resources-EarthEnvironmental Sciences * Lufeng Zhang [email protected] 1
The Unconventional Natural Gas Institute, China University of Petroleum at Beijing, Beijing 102249, China
2
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum at Beijing, Beijing 102249, China
workover operation (Civan 2015; Su et al. 2018; Peng and Li 2018). The permeability of gas- or oil-producing formation will d
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