印尼厘茂油田INJ-02B井密闭取心复杂情况处理与分析

Handling and analysis of downhole troubles during sealed coring in Well INJ-02B in Limau Oilfield of Indonesia

INJ-02B井是印尼厘茂油田第一口取心井,设计井深1500 m,取心段长90 m。对比电测发现,取心段上部的井壁出现坍塌和缩径,导致下取心钻具失效。取心钻进过程钻遇极松软地层,岩心强度不够,无法成岩,造成堵心。同时由于松软地层钻速较快,地面无法判断是否已经堵心,进而导致磨心。经现场分析,在井径不规则井段,下入牙轮钻头划眼,确保井径规则,下钻至井底时采取转盘高速旋转以破碎大块岩屑,同时打高黏钻井液将大块岩屑携带出井筒,确保井底清洁。再通过分析取心钻时,采用适合于松散地层的低钻压、低转数和低排量的钻进参数来提高岩心的成岩率,从而降低堵心和磨心的风险。由于现场及时采取了以上技术措施,确保了该井取心的整体收获率为90.37%。该技术适用于印尼厘茂油田井塌井和松软地层的密闭取心的施工。

Well INJ-02B was the ifrst cored well in Limau Oilifeld of Indonesia. The design well depth was 1 500 m and the coring section was 90 m. Compared with electric logs, it was found that the upper part of the coring section had collapsed and shrunk, leading to failure of running coring tools. Very soft formation was encountered during coring drilling, so the core strength was not enough to form a rock, hence blocking the core. Meanwhile, the ROP in soft formation was fast, so it is impossible to determine on surface if the core was blocked or not, hence leading to core grinding. Field analysis shows that roller bit should be run to ream the hole in irregular hole intervals to ensure regular and consistent hole size,When the bit was lowered to the bottom, large blocks of cuttings were broken by the rotary table at high RPM. At the same time, high-viscosity drilling lfuid was pumped down to carry the large cuttings out of the hole to ensure hole cleaning. Then through analyzing the coring drilling time, the core-forming rate was improved using such drilling parameters as low WOB, low rpm and low displacement which were suitable for loose formations, so as to reduce the risk of core blocking and core grinding. The above measures were taken in a timely manner, so the overall core recovery rate of this well was up to 90.37%. This technique is applicable to sealed coring in collapsed wells and soft formations in Limau Oilifeld of Indonesia.