靖边气田井壁失稳原因分析与建议

REASONS ANALYSIS OF HOLE INSTABILITY IN JINGBIAN GAS FIELD

靖边气田目的层埋藏较深,钻井周期长,斜井段穿越地层极容易发生井壁失稳和井下复杂。在分析导致靖南区块斜井段坍塌地质因素基础上,对斜井段易坍塌地层取样,通过对岩样全岩矿物、微观结构及理化性能等方面分析,得到岩石组分主要以石英、长石、伊利石等组成的硬脆性泥质砂岩,黏土含量相对较高,而且黏土组成主要以伊蒙间层为主,其次是伊利石;岩石孔隙复杂,发育成熟,有裂缝存在;同时岩心矿物阳离子交换容量较高,水化膨胀及分散较弱。通过分析认为井眼坍塌的内因是节理、微裂缝发育,胶结疏松,易水化;外因是水的侵入和外力作用。提出了防塌技术对策。

The Jingbian gas reservoir has the features of deep buried depth,long drilling cycle,borehole instability and downhole complex in drilling inclined well section. To solve the problems,based on analyzing the geological factors resulted in hole collapse in inclined well section,the formation sampling from the inclined section was done and the mineral composition,microtexture and physical and chemical property of the rock sample were analyzed. The analysis results showed that the rock sample composed of qartz,feldspar,illite and others was typical hard-brittle argillaceous sandstone,the content of clay mineral was relatively high,rock pore was complex. Meanwhile,cation exchange capacity in core mineral was high,hydrous disintegration in the rock samples was weak. By the analysis,the internal factors of hole collapse were found,i. e. developed fissuring and micro-fracture,loose cementing,easy hydrating etc.,and the external factors were the combined effect of both water intrusion and external force during drilling. In the end,the anti-sloughing technical measures were brought forward.