摘要
在考虑试验岩样尺度效应的基础上,进行的模拟地层条件下钻井液对岩石力学性质影响的试验研究结果表明:经钻井液处理后的25mm×25mm岩样的抗张强度高于未经钻井液处理的50mm×50mm岩样,且处理后的岩样抗张强度均高于未处理的岩样。对于钻井液处理前后同尺寸的岩样,由于试验岩样中泥质软颗粒含量高低不同,在孔隙度小于2.5%时,孔隙度越小,处理前后的抗张强度相差越大,且处理前的岩样抗张强度比处理后的岩样大4MPa左右;在孔隙度大于2.5%时,钻井液处理前后的岩石抗张强度趋于一致。在模拟地层条件下,钻井液处理后的岩样抗压强度和弹性模量显著下降,泊松比增大。岩石矿物中的泥质黏土矿物遇到钻井滤液后产生软化效应,致使岩样呈现:经钻井液处理时间越长,其抗压强度和弹性模量下降越多的趋势。
On the basis of size effects of trial rock,the effects of drilling fluid on the mechanical properties of rocks were investigated experimentally under the simulated formation conditions. The results showed that rock tensile strength of sample with a diameter of 25 mm and a length of 25mm treated by drilling fluid was higher than that of untreated rock samples with a diameter of 50mm and a length of 50mm. Because of different content of shale in trial samples, difference of tensile strengths of samples before and after trea ted by drilling fluid got greater and porosity of sample got smaller as the porosity was less than 2.5%. Difference of tensile strengths of treated and untreated samples was about 4 MPa. As porosity of rock sample was larger than 2.5 %, tensile strength of treated sample was nearly consistent with that of the untreated samples. Under simulating rock formation conditions, the compressive strength and Young＇s modulus of the sample treated by drilling fluid decreased significantly,the Poisson＇s ratio increased. The longer treatment time of samples would result in the more reduction of compressive strength and Young＇s modulus,because the shale or clay in rock sample would get soft by the drilling fluid filling.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2008年第1期135-138,共4页
Acta Petrolei Sinica
基金
中国石油化工股份有限公司科技项目“川西特低渗透深层砂岩气藏压裂技术研究与应用”(P02034-T01)部分成果
关键词
岩石力学性质
尺度效应
钻井液
试验评价
抗张强度
致密储层
mechanical properties of rock
size effect
drilling fluid
trial evaluation
tensile strength
compact reservoir
