长北气田本着安全环保的理念，近年来不断重复使用低伤害钻完井液（DIF），使得一些不易清除的黏土颗粒不断在钻井液中积累，导致钻井液中分散黏土含量（MBT）不断升高，在液柱的高压差下，使钻井液中分散很细的黏土微粒进入储层，使储层孔隙进一步缩小，水锁加剧，导致产量降低。针对这一难题，主要从改变储层表面性质着手，研制出了洗井液NDF－1，该洗井液使低渗砂岩气藏由强亲水变为弱亲水，消除储层毛管力，溶解进入部分固相，拆散堵塞，从而提高气驱水效率，消除固相伤害。室内试验表明，洗井液NDF－1可以使现场DIF伤害后岩心渗透率恢复率得到明显提高，效果优于酸液，并且可以完全克服室内配制DIF钻井液给岩心造成的伤害。

YB365-H06井是延113-延133区块一口单分支水平井，水平段设计1000m，采用和壳牌长北相同的钻井液体系（无土低固相低伤害钻井液体系）设计施工。现场施工过程中钻遇长段炭质泥岩造成井壁失稳，为保证井壁稳定，通过转换体系提高钻井液的抑制封堵性能，研究出适合该区块水平段山23地层的钻井液技术，优化后的钻井液具有热稳定性好、失水低、润滑性能优良、较高的抑制防塌性能等特点。YB365-H06井的成功施工对该区块水平井开发具有重要的指导意义。

长北气田采用裸眼完井方式,钻进中钻井液跟储层的接触时间长,为了减小在水平段钻进过程中钻井液液相和固相侵入对储层的伤害,模拟长北气田地层环境做钻井液对储层的伤害实验,研究出一套适合长北水平段山2气层的储层保护技术.现场5口井的应用结果表明,钻进过程中钻井液对储层的伤害很小,CB8-3完井投产后获得超过230×104m3/d的工业气流,创造单井产量最高记录.表明对裸眼水平段的储层保护钻井液技术取得明显效果.

With the rapid growth of market demand for natural gas, how to successfully develop the rich CBM reservoir in Ningwu basin becomes an important subject in unconventional gas reservoir development.It is one of the key factors to sci-entifically determine a suitable drilling fluid density window by combining with the crustal stress state, the parameters of formation pore pressure and formation strength, as well as angle of deviation and azimuth angle in order to realize effective and safe coal-bed methane industrialization development in Ningwu basin.The finite element model of No.9 coal seam in Ningwu basin is established by ANSYS software, the influence rule of hole enlargement ratio is analyzed in the conditions of different crustal stress directions and different well inclination, by which the optimized range of mud density is obtained to control coal seam collapse and reduce complex prescription, and the support for research on improvement of drilling effi-ciency and comprehensive benefit of CBM in NingWu basin is found.

目前长北气田已进入三期井丛开采,大部分井丛分布在长北气田区块的边缘地带,储层段富含炭质泥岩、泥岩以及凝灰岩,井壁坍塌掉块和遏阻卡钻问题突出,已有的研究表明泥岩水化膨胀是造成水平段井壁失稳的主要原因,因此提出通过提高ASS-1钻井液体系密度和增强钻井液体系抑制性来解决这一问题,但是常规加重剂石灰石粉,虽能提高钻井液密度,但不能满足增加抑制性的要求,为此研发出了一种新型的钻井液用液相加重剂NS-1.室内着重研究了NS-1的加重能力,与酸溶暂堵钻井(完井)液ASS-1体系的配伍性、抑制性、腐蚀性以及对储层的影响.研究结果表明:NS-1具有较强的加重能力,浓度20％的NS-1即可将ASS-1体系加重至1.18g/cm3以上,同时还具有与ASS-1体系配伍性好、抑制性强、腐蚀速率低和低污染等优点.钻井液用液相加重剂NS-1的研发不仅很好解决长北区块长水平段泥岩安全钻进问题,也可为其它油田相似区块钻井液液相加重剂的研发提供借鉴.

How to develop the rich CBM resource now becomes an important project in China. The wellbore insta-bility is a key factor restricting CBM economical development. According to rock mechanics the mechanical charac-teristics of coal bed is critical factor for CBM wellbore stability, the study of the static mechanical characteristics has only developed in a limited level in China recently, this paper makes the systematic study on the mechanics of coal bed in Ningwu basin, got the extension and compressive strength, calculated the internal friction angle and the cohesion, built the power law relationship for longitudinal wave and transverse wave and also found out the linear relation between dynamic elastic parameters and static elastic parameters. It gives a technical method on how to get mechanics characteristics of formation on the basis of dynamic elastic parameters obtained from acoustic logging.

长北气田采用裸眼完井方式,水平段钻进过程中钻井液跟储层的接触时间长,液相和固相侵入对储层的伤害严重.介绍了长北气田储层特征,模拟长北气田地层条件进行了钻井液储层伤害实验,分析其储层伤害因素,研究出一套适合长北气田水平段山2气层的保护储层钻井液,现场5口井的应用结果表明钻进过程中钻井液对储层的伤害很小,CB8-3井完井投产后获得超过230×104 m3/d的工业气流,创造单井产量最高记录.所研究的储层保护钻井液能很好地解决储层伤害问题.

CB3-3是榆林长北气田的一口双分支水平井,该井第二条分支水平段安全钻达2 300m,创长北气田水平段最长纪录.新型的KCl聚合物钻井液体系和无土低固相低伤害钻完井液体系分别在该井斜井段、水平段进行了应用及评价.实验结果表明,新型的KCl聚合物钻井液抑制性强、润滑防卡性能好、携砂能力强,能够保证有效快速钻进,能够确保分支井二开裸眼井段的稳定性;无土低固相低伤害钻完井液体系具有稳定性良好、密度低、失水低、润滑防卡性能优良、能有效生物降解等特点,具有对储层的低伤害性,是一种新型高效的钻完井液体系.

C B17-2井为长北气田的一口双分支水平井，承担着该气田增产稳产的重要任务。为进一步加快开发速度、缩短建井周期，在原来二开氯化钾钻井液的基础上，通过优化钻井液流变参数，合理地控制密度，提高抑制性等一系列技术措施，有效地控制了泥页岩水化分散和地层造浆，保证了良好的井壁稳定性，定向造斜钻进与下套管均顺利，只用三趟钻就完成进尺2721米，平均机械钻速达8.13米/小时，刷新了长北项目二开钻井的纪录，为该区块二开快速钻进提供了宝贵的经验和有力的技术支持。

CB8-3井是壳牌长北项目C8井丛的一口双分支水平井,目的层在山西组砂岩层。针对该井所在区块复杂地层特点,结合近几年的现场经验总结和大量的室内试验研究,在CB8-3井二开121/4〞井眼钻进中使用SJY-1强抑制钻井液体系,该体系具有强的防塌抑制性,扭矩和摩阻低,润滑性能好,井眼净化能力强,起下钻无阻卡现象,下套管顺利,SJY-1强抑制钻井液体系在CB8-3井的成功应用为该区块二开复杂井段钻进提供了宝贵的经验和有力的技术支持。

Changbei gasfield belongs to tight gas reservoir. In the drilling process, the invasion of drilling fluids is one of the main reservoir damage factors. To reduce the invasion of drilling and completion fluids, studies were mainly focus on temporary plugging and wettability change of reservoir rock surface, and a type of NDW clay-free low damage drilling fluid was developed. The fluid had effective protection for gas reservoir because its average damage ratio to the pay-zone is only 11.25%, tested under reservoir conditions. The fliud had good temporary plugging, excellent inhibitive ability and high lubricity. In the whole drilling of horizontal interval in well CB8-3, the cumulative horizontal interval length using the fluid is 4 388 m, and the borehole is always kept clean, with no blockage and no pipe-sticking during tripping, and no sand setting in downhole. Moreover, more than 240 m shale was stable and the production of 230×104 m3/d in this well was obtained, which created the new record of highest individual production rate in onshore low permeability gasfield in China.