花场、朝阳区块流沙港组井壁稳定性研究

Wellbore Stability of Liushagang Formation in Huachang and Chaoyang Oilfield

花场、朝阳区块位于福山凹陷,该处区块构造运动强烈,井下多次发生起下钻遇阻卡、坍塌等复杂事故,需对该区块井壁失稳机理进行分析,研究断层对井壁稳定的影响。通过钻井资料分析流沙港组地层井壁失稳特点及机理,并依据单一弱面准则,建立四压力剖面及安全钻井液密度窗口。结果表明,地层失稳的主要是由于断层处沿弱面剪切滑移;钻井液沿层理裂隙侵入,使得地层强度降低。Huachang and Chaoyang blocks are situated in the Fushan depression, an area characterized by intense tectonic activity, leading to frequent and complex downhole drilling incidents such as blockages, jams, and collapses. It is imperative to analyze the mechanisms of well-wall destabilization in this block and investigate the impact of faults on well-wall stability. Drilling data was utilized to conduct an analysis of the characteristics and mechanisms of well wall destabilization within the Liushagang Group formation. Additionally, a four-pressure profile and a safe drilling fluid density window were established based on the single weak surface criterion. The results indicate that the primary cause of formation destabilization is shear slip along the weak face at the fault, while drilling fluid intrusion along laminar fissures contributes to a reduction in formation strength.