辽东湾探井用改性天然高分子钻井液技术

DS4井是一口位于渤海北部辽东湾海域的区域探井。针对DS4井裸眼段长、地质条件复杂、钻遇油气层位多的情况，在对钻井液抑制性、封堵性、保护油气层作用机理进行分析的基础上，对改性天然高分子钻井液进行了配方优选。实验结果表明，在改性天然高分子钻井液中引入强抑制剂AP-1和封堵剂DLP后，钻井液具有良好的抑制性和封堵性，防止了DS4井上部明化镇组、馆陶组高渗透地层的漏失，在较低的密度下确保了下部东营组泥岩地层的井壁稳定，实现了安全快速钻井；具有优良的润滑能力，在DS4井二开裸眼段长3131 m、位移大（1060 m）、最大井斜达到34.5°的情况下，成功地实现了电测一次成功率100%；钻井液具有低荧光特性，能够及时地发现油气层；具有优良的油层保护效果，DS4井在东营组发现了良好的油气显示，并在试油阶段获得了高产的工业油流。 

Modified Natural Polymer Drilling Fluid Used in Exploration Wells in the Gulf of Liaodong

The well DS4 is an areal exploration well located in the offshore Gulf of Liaodong in the north Bohai Sea. The well DS4, a long open-hole well, penetrated formations with complex geology and many oil and gas bearing zones. Based on the studies on the inhibitive capacity and plugging capacity of the drilling fluid, as well as reservoir protection mechanism, a modified natural polymer drilling fluid was optimized. The results of the laboratory experiments have revealed that the inhibitive capacity and the plugging capacity of the drilling fluid are greatly enhanced after treatment with the strong shale inhibitor AP-1 and the plugging agent DLP. Using this modified natural polymer drilling fluid, mud losses previously occurred in drilling the highly permeable Minghuazhen formation and Guantao formation were minimized, and the borehole wall instability in drilling the lower Dongying formation (shales) was brought under control with lower mud weights, realizing safe and fast drilling. This drilling fluid has good lubricity; in the second interval, which has length of 3,131 m, horizontal displacement of 1,060 m and well angle of 34.5℃, the wireline logging was 100% successful, with no repetition. The drilling fluid has low fluorescence, which is helpful in pinpointing pay zones accurately. The drilling fluid has good reservoir protection ability; the well DS4 had good oil shows, and high production rate was obtained during well testing.