Spontaneous imbibition in igneous rocks: effect of KCl concentration, confining pressure, and imbibition direction
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Spontaneous imbibition in igneous rocks: effect of KCl concentration, confining pressure, and imbibition direction Changlin Zhou1 · Li Li1 · Rong Zeng1 · Weihua Chen1 · Yuxuan Liu2 Received: 6 April 2020 / Accepted: 27 August 2020 © The Author(s) 2020
Abstract Understanding spontaneous imbibition helps to determine the fracturing fluid volume and optimize the flowback design. At present, many studies have mainly focused on shale, but few on igneous rocks. As such, in this study, imbibition experiments were conducted on igneous rocks. The effects of KCl concentration, confining pressure, and imbibition direction on the spontaneous imbibition were systematically investigated. This study then introduces a new imbibition capacity index. The results show that KCl concentration has certain inhibitory effects on igneous rock imbibition, which reduce the absorption of clay minerals to liquid. Different imbibition directions result in distinct imbibition volumes. The co-current imbibition process is similar to fluid leak-off, but this rule is not satisfied in countercurrent imbibition, the n of which is fitted as 0.1.0.3. Increasing the confining pressure will slightly decrease the imbibition capacity of igneous rock. Rock imbibition causes a decrease in the surface hardness and physical properties of igneous rock, and increasing the KCl concentration in the fluid will effectively hinder clay swelling. Keywords Spontaneous imbibition · Hydraulic fracturing · KCl concentration · Confining pressure · Imbibition direction
Introduction Unconventional reservoirs have become the focus of research seeking to explore and develop oil and gas (Zou et al. 2018). One of the key technologies for unconventional oil and gas development is the multistage fracturing of horizontal wells (Huang et al. 2019; Al-Fatlawi et al. 2019; Gao et al. 2018; Sobhaniaragh et al. 2016). In the multistage fracturing process, a large amount of liquid needs to be pumped into the formation, but field practice has shown that a large amount of liquid remains underground. This has attracted attention, and scholars have conducted much research on fracturing fluid retention, the focus of which is spontaneous imbibition. Spontaneous imbibition refers to the process of absorption with no pressure driving the phase into the rock.
* Yuxuan Liu [email protected] 1
Engineering Technology Research Institute, Southwest Oil and Gas Field Company of CNPC, Chengdu 610031, China
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
2
Dehghanpour et al. (2012) studied the relationship between illite content, quartz content, and the amount of spontaneous imbibition. Both water absorption and oil absorption were positively correlated with illite content and negatively correlated with quartz content. At the same time, the effects of kerosene and low-concentration aqueous solutions on spontaneous imbibition were studied. The results showed that the ratio of
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