强抑制性水基钻井液在长宁区块页岩气水平井中的应用

Application of strong-inhibition water-based drilling fluid in shale gas horizontal wells of Changning Block

近年来,随着新环保法的颁布和环保观念的增强以及降低钻井成本的压力,页岩气储层井段常采用油基或合成基钻井液钻进使用范围越来越小,研发并应用页岩气水基钻井液成为当前开发页岩气的热点和重点攻关技术。通过分析页岩气储层地质特征,针对其页理发育、孔隙度低、渗透率低、微裂缝发育、强分散性、易剥落掉块和垮塌的特点,以及长水平段深井钻井防黏卡、强封堵防塌、低摩阻、良好润滑性等工程需求,以抑制性、封堵能力、润滑性和流变性为核心和重点研究对象,自主研发出一套页岩气水基钻井液配方,并在四川盆地长宁页岩气区块试用。应用结果表明,该钻井液配方精练,维护处理简单,性能稳定,具有优良的抑制性、封堵性、润滑性和流变性,以及滤失量低等特点,完全满足长宁区块页岩气水平井地质和工程需求,为优质安全快速钻井提供了有力的技术支持。该页岩气水基钻井液可取代目前页岩气钻进中常用的油基和合成基钻井液,既可节约钻探成本,又能大幅降低环保压力,具有广阔的推广应用前景。

As new environmental laws are enacted, environmental protection concept is enhanced and the pressure oI low cost urlll- ing is increased in recent years, the oil-based or synthetic based drilling fluids which were commonly used in shale gas reservoirs are decreasingly applied, while the research, development and application of water-based drilling fluid is becoming the hot spot and key technology for shale gas development. Shale gas reservoirs are geologically characterized by lamellation, low porosity, low permeabil- ity, microfractures, strong dispersion, easy denudation and collapse. Considering the geologic characteristics of shale gas reservoirs, together with drilling engineering requirements of long horizontal sections in deep wells, such as sticking prevention, strong plugging for collapse prevention, low friction and good lubricity, a set of shale gas water-based drilling fluid formula was independently de- veloped with inhibitive, plugging, lubricating and rheological properties as the core and key research objects. It was tried out in the Changning shale gas block in the Sichuan Basin. This drilling fluid formula is terse and it can be maintained and treated simply. Its property is stable with good inhibitive, plugging, lubricating and rheological properties and low fluid loss. It can fully meet the geo- logic and engineering requirements of shale gas horizontal wells in Changning block. It provides the technical support for efficient, safe and rapid drilling. This water-based drilling fluid for shale gas development can take the place of oil-based or synthetic based drilling fluids which are commonly used for shale gas drilling area. With this system, the drilling cost is cut down and the pressure of environmental protection is alleviated greatly. It presents the promising prospect of broad popularization and application.