The Study on Time-dependent Permeability of Fractured Core under Effective Stress
The permeability of fractured core decreases not only with raising the effective stress, but also with time. In this paper the core flow test had been conducted by use of the outcrop with different fracture width from western Sichuan basin, the test fluids were nitrogen and brine (3%KC1). The study shows that the decrease of permeability is up to almost 48% and the time of equilibrium is more than 1.5 hour under the 3MPa effective stress. But when the effective stress is 10MPa, the decrease was below 30% and the time of equilibrium is less than 1 hour. And the reduction of time-dependent permeability tested with gas (nitrogen) is below 15% when effective stress is 3MPa; however the permeability tested by brine decreases as much as 48% under the same effective stress. The study analyzes that the saturated core fracture has been propped by micro-bulges, which are easier to be embedded into each other and slide. In the process of fracturing, the fracture surface become weak consolidation, this can cause fine migration. The hydrated clay minerals on the fracture surface have a buffer effect, so the stress could not be fully loaded immediately. In addition, some minerals such as feldspar on the fracture surface could be dissolved during the brine flows through the fracture under higher effective stress; this can cause the aperture to become smaller. During the development of the reservoir, the accumulated water in the fracture and the working fluids should be withdrawn as quickly as possible. And in the processes of formation damage assessment, the effect of time-dependent permeability should be eliminated as much as possible.
permeability time-dependent effective stress fracture micro-bulges pressure solution
DU Xinlong KANG Yili YOU Lijun
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, P.R.China, 610500
国际会议
2009 International Forum on Porous Flow and Applications(第十届全国渗流力学学术会议)
武汉
英文
535-540
2009-04-26（万方平台首次上网日期，不代表论文的发表时间）