提高川西南地区钻井速度的有效途径

EFFECTIVE WAY TO RAISE DRILLING SPEED IN SOUTHWEST SICHUAN REGION

四川地质构造复杂 ,纵向上高低压力系统交错分布 ,横向上炭酸盐岩裂缝系统展布又难以预测 ,因而钻井液密度很难做到自上而下科学地平衡钻井。在实际工作中往往考虑更多的是地层压力梯度异常带来的井喷事故 ,为了避免这类事故 ,经常采用构造上已钻井出现过的最高压力梯度来设计钻井液密度 ,这种做法对多数井是过平衡钻井 ,严重影响机械钻速 ,造成钻井速度慢 ,钻井成本高。文章以川西南地区钻井资料分析为基础 ,找出了影响钻井速度的因素 : 2 15 .9mm井段是影响整口井钻井速度的主要井段 ,如果在 2 15 .9mm井段提高钻井速度 ,一口井的钻井周期就可加快。提高川西南地区的钻井速度的两个有效技术途径 :一是平衡钻进 ,二是高密度条件下使用螺杆钻具带巴拉斯钻头钻井。在几个构造多口井的实践中取得了良好的技术、经济效益 。

The geological structures in Sichuan are complex:the high pressure system and low one being crisscross distributed longitudinally and the spread of the carbonate fracture systems being difficult to be predicted horizontally,thus,the drilling fluid density is difficult to meet the requirements of the scientific drilling under balanced pressure from above to below.In the practice,what is considered even more is the blowout accident caused by the abnormal formation pressure gradient.In order to avoid this kind of accident,the maximum pressure gradient appeared in the well drilled on the structure is often adopted to design the drilling fluid density,but this method is a drilling method under overbalanced pressure for the majority of wells,which seriously affects the penetration rate and causes low drilling speed and high drilling cost.In this paper,on the basis of analyzing drilling data in Southwest Sichuan region,the factors affecting the drilling speed is found,namely,the hole interval of 215.9 mm is that influencing the drilling speed of whole well,if the drilling speed in this interval is raised,the drilling cycle of whole well can be quickened.The two effective technical ways to raise the drilling speed in Southwest Sichuan region,i.e.1)drilling under balanced pressure and 2)drilling by use of positive displacement drill with ballas bit under the condition of high density,are put forward,which obtained a good technic economic benefits in drilling many wells on several structures.The matters needing attention for well doing above mentioned two works are proposed also.