CAJ | 학술논문

为了解决西部超深硬脆性泥岩地层侧钻过程中井壁易垮塌的难题，从矿物特征及钻井液作用下地层强度的变化规律出发，确定了井壁失稳原因，考虑了层理面产状、井眼轨迹及地应力的综合影响，根据桑塔木组井壁围岩强度破坏条件建立了造斜井段井壁失稳地质力学模型。利用提出的井壁稳定力学模型分析可得，TKX‐CH井侧钻段泥岩造斜初期坍塌压力当量密度为1.22 kg／L ，实钻采用钻井液密度1.12 kg／L ，井下掉块严重；井斜角达到58°时，将钻井液密度降至1.11 kg／L ，井下掉块即得到抑制。现场试验表明，相同井斜角和侧钻方位角条件下，随着差应力比值的增大以及泥岩裸露在钻井液中时间的增长，维持井壁稳定的钻井液密度增大。研究认为，钻井设计时应根据地应力状态优选合理的造斜方位，以有效规避地层井壁围岩坍塌失稳风险高的井段，降低安全钻进风险。
위료해결서부초심경취성니암지층측찬과정중정벽역과탑적난제，종광물특정급찬정액작용하지층강도적변화규률출발，학정료정벽실은원인，고필료층리면산상、정안궤적급지응력적종합영향，근거상탑목조정벽위암강도파배조건건립료조사정단정벽실은지질역학모형。이용제출적정벽은정역학모형분석가득，TKX‐CH정측찬단니암조사초기담탑압력당량밀도위1.22 kg／L ，실찬채용찬정액밀도1.12 kg／L ，정하도괴엄중；정사각체도58°시，장찬정액밀도강지1.11 kg／L ，정하도괴즉득도억제。현장시험표명，상동정사각화측찬방위각조건하，수착차응력비치적증대이급니암라로재찬정액중시간적증장，유지정벽은정적찬정액밀도증대。연구인위，찬정설계시응근거지응력상태우선합리적조사방위，이유효규피지층정벽위암담탑실은풍험고적정단，강저안전찬진풍험。
To solve the wellbore instability problem of a deep sidetracking well in hard‐brittle mud‐stone strata of w est China ,this paper indicated the mechanism of w ellbore instability considering the effects of both minerals and drilling mud on rock compressive strength .Based on failure condition of wellbore ,a model of well instability was built considering the contributions of bedding plane occurrence ,in‐situ stress , and well trajectory ,etc .The calculations of this model for the sidetracking mudstone segment in Well TKX‐CH showed that the collapse pressure is 1.11 kg/L .Serious rock‐collapse happened in practice when drill‐ing mud was 1.12 kg/L .This situation improved as the drilling mud density decreased to 1.1 kg/L ,when the deviation angle reached to 58° .When the sidetracking orientation and deviation angle are constant ,the density of drilling mud to keep well stable increases as the ratio of stress difference increases and as expo‐sure time of mudstone inside drilling mud increases .Therefore ,in order to decrease the risk of borehole in‐stability ,in‐situ stress ,bedding planes and exposure time of mudstone should be considered systematically in drilling desig n .