提高渤海中深层机械钻速技术应用

渤海A油田主力储层为太古界潜山地层，岩性为片麻岩，目的层垂深超过4 000 m，上部孔店组地层发育一套砾径超过7 mm的含砾砂岩，常规PDC钻头钻进，钻头崩齿严重，更换频繁；牙轮钻头机械钻速低，磨损严重，钻井周期增加导致裸眼浸泡时间加长，上部地层垮塌频发，严重制约油田开发。通过对测井资料回归并校核岩心强度，确定地层可钻性级值剖面，为钻头优选提供了理论依据，并分析了多种提速工具的优劣。孔店组非均质含砾砂岩地层采用一体化复合冲击工具，降低了崩齿导致的钻头早期破坏；潜山片麻岩地层引入扭冲工具配合忍者齿PDC钻头钻进有效提高机械钻速，使单只钻头进尺大大增加，实现了渤海中深层钻井的提速。在A油田勘探过程中形成了渤海中深层优选钻头技术，该技术在钻井实践中得到了检验，降低了中深层的开发门槛，实现了勘探开发费用的降低，也为未来渤海中深层油田的开发提供了经验和技术支持。

Application of ROP improvement technology in middle and deep strata of the Bohai Sea

The principal reservoir of Bohai A Oilfield is the Archean buried-hill formation and it is lithologically composed of gneiss. The vertical depth of the target layer is over 4 000 m. A set of pebbled sandstones with pebble size over 7 mm are developed in the Kongdian Formation in the upper part. When the conventional PDC bit is used, its teeth are broken up seriously and it is replaced frequently. When the cone bit is adopted, it is wore seriously with low rate of penetration (ROP) and long drilling cycle, which extends the soaking time of open hole, leading to frequent collapse of the upper strata. As a result, the development of the oilfield is restricted seriously. In this paper, the formation drillability grade profile was determined by regressing the logging data and checking the core strength, so as to provide the theoretical basis for bit selection. Then, the advantages and disadvantages of various ROP improvement tools were analyzed. The integrated complex impact tool was adopted in the heterogeneous pebbled sandstones of Kongdian Formation, and consequently the early bit damage caused by tooth breakage was reduced. The torsional impact tool, combined with Ninja-tooth PDC bit was introduced into buried-hill gneiss formation, and consequently the ROP was improved effectively and the single-bit drilling footage is increased significantly. Thus, the improvement of ROP in middle and deep strata in the Bohai Sea is realized. To sum up, the bit selection technology for middle and deep strata in the Bohai Sea is developed in the exploration process of Bohai A Oilfield. This technology is verified in the drilling practice. It decreases the development threshold of middle and deep strata, cuts down the exploration and development costs, and provides the experience and technical support for the future development of middle- and deep-seated oil fields in the Bohai Sea.