Abstract
Steering acid fracturing is a technique that improves the conductivity of carbonate reservoir. It is widely used in a carbonate reservoir. However, due to the lack of comparative experiments, the application of steering acid to improve the fracturing results is still unknown. Therefore, a series of true triaxial acid fracturing experiments were conducted to study steering acid fracturing in carbonate reservoir. The carbonate specimens used in the experiment were from the Qixia group and Dengsi Member in Sichuan, China. In this study, slick water, cross-linked gel, and self-generating acid were used as ahead fluid to cooperate with steering acid. Experimental results show that (1) the low-viscosity ahead fluid with steering acid can result in more complex fractures; (2) the complexity of fractures is influenced by natural fracture and the viscosity of the ahead fluid; and (3) based on the 3D scanning results of the fracture surface, different ahead fluids will lead to different corrosion results. This study provides useful suggestions on steering acid fracturing design and physical simulation experiments.
Highlights
Various development techniques applied to unconventional reservoirs such as low-permeability reservoirs have received increasing attention [1,2,3,4,5]
Natural fractures were roughly marked before the experiment
There was a natural fracture about 10 cm from the wellbore, which was parallel to the wellbore and extended from the upper surface of the rock specimen to the lower surface
Summary
Various development techniques applied to unconventional reservoirs such as low-permeability reservoirs have received increasing attention [1,2,3,4,5]. Carbonate reservoirs have lower permeability and porosity as compared to conventional reservoirs, which results in challenges for the conventional development methods [6]. Compared with normal hydraulic fracturing, it is hard to control the penetration distance caused by acid solution in acid fracturing. Hou et al reported a successful utilization of alternating acid fracturing, which used self-generating acid as the ahead fluid to penetrate and cool reservoir and gelled acid to deeply penetrate carbonate reservoir (FAN, et al 2018). These studies provide a reference for experiment design. The study provides a way to digitally process experimental results
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