College of Science, Heilongjiang Bayi Agricultural University, Daqing, 113001, China.
College of Petroleum Engineering, China University of Petroleum (East China), Qingdao, 266580, China.
Environ Sci Pollut Res Int. 2022 Mar;29(12):17682-17694. doi: 10.1007/s11356-021-17045-w. Epub 2021 Oct 21.
As an important working fluid in tight shale reservoir, supercritical CO has been proven to improve oil recovery efficiently. However, the high filtration caused by the low viscosity of pure supercritical CO hinders its development. The research objective of this investigation is to explore the filtration of supercritical CO with a branched siloxane (BTMT) as a CO thickener and filtration-reducing agent, and analyze the influence level of some parameters about rock core and chemicals on the CO filtration in the tight shale reservoir by using response surface method (RSM). The results demonstrate that the rising temperature causes a gradually increasing filtration, but filtration coefficient (f) decreases with increasing the pressure difference P, injection speed, and thickener concentration. The thickener concentration is the factor that causes the greatest change in filtration coefficient according to the response surface method, and the injection speed has the smallest effect on the filtration. The viscosity of fracturing fluid is the main characterization parameter leading to change of filtration coefficient, all factors that contribute to increasing the viscosity of the fracturing fluid will lead to a reduction in the filtration coefficient and an enhanced oil recovery. In addition, the adsorption and reservoir residue of BTMT on low-permeability shale were subordinated to a Langmuir monolayer theory, and a low residual of BTMT in shale can prevent thickeners and fracturing fluids from damaging shale reservoirs. The improvement of thickener and CO fracturing technology provided a basic reference for shale exploitation, greenhouse effect, and reservoir protection.
作为致密页岩储层中的一种重要工作流体，超临界 CO2 已被证明可有效提高采油率。然而，由于纯超临界 CO2 粘度低，导致其过滤性能较差，从而阻碍了其发展。本研究的目的是探讨以支化硅氧烷（BTMT）作为 CO2 增稠剂和降滤失剂时的超临界 CO2 过滤情况，并通过响应面法（RSM）分析一些关于岩心和化学物质的参数对致密页岩储层中超临界 CO2 过滤的影响程度。结果表明，升高温度会导致过滤逐渐增加，但随着压力差 P、注入速度和增稠剂浓度的增加，过滤系数（f）减小。根据响应面法，增稠剂浓度是导致过滤系数变化最大的因素，而注入速度对过滤的影响最小。压裂液的粘度是导致过滤系数变化的主要特征参数，所有增加压裂液粘度的因素都会导致过滤系数减小，从而提高采油率。此外，BTMT 在低渗透页岩上的吸附和储层残留服从 Langmuir 单层理论，BTMT 在页岩中的低残留可以防止增稠剂和压裂液对页岩储层造成损害。增稠剂和 CO2 压裂技术的改进为页岩开采、温室效应和储层保护提供了基础参考。
