Formation damage mechanism and control strategy of the compound function of drilling fluid and fracturing fluid in shale reservoirs

For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.

天然气欠平衡钻井技术在井浅2井的应用

天然气欠平衡钻井就是在钻开产层前采用天然气作为钻井介质,替换普通泥浆进行钻井作业,在钻井过程中井筒气柱压力低于地层压力,允许地层流体进入井筒,没有钻井液滤液和有害固相微粒进入地层。它与其它欠平衡钻井作业方式相比,具有鲜明的技术特点和独特的技术优势,是一种对于产层少污染的非常规钻井方式,是真实评价和最好保护油气层的最佳钻井方法。文章结合井浅 2 井,重点介绍了有关天然气欠平衡钻井的一些关键技术,主要包括储层特征、井身结构、钻具组合、气举、天然气钻进技术、不压井带压起下钻技术、不压井带压下油管技术等,并列举了天然气欠平衡钻井在该井所取得的主要技术成果。井浅 2 井首次在南井构造须家河组获得油气储量,实现了该构造须家河组油气勘探开发的重大突破。为勘探开发川南水敏伤害严重的低压碎屑岩储层找到了一种有效的技术手段。

聚合醇防塌润滑剂PGP-3及其钻井液的应用

开发了一种钻井液用聚合醇防塌润滑剂PGP 3。岩屑回收和岩心浸泡实验结果表明 ,PGP 3的抑制性能优于KCl水溶液 ,PGP 3与KCl合用时抑制效果更好。在膨润土抑制实验和极压润滑系数测定中确定PGP 3的最佳用量为 3%。 3%PGP 3处理的 6 %粘土浆的流变参数 (AV ,PV ,YP)和滤失量 ,随滚动温度的升高 (10 0～ 2 0 0℃ )而升高 ,与SMP相比 ,其耐温性良好。在膨润土浆中PGP 3可与低粘CMC、高粘CMC ,SMP ,PSC等处理剂配伍。使用PGP 3的钻井液最佳配方为 :3%PGP 3+0 .2 %PAM +2 %SMP +1%PSC +0 .5 %SJ 1+0 .1%NaOH。最佳配方PGP 3钻井液污染后岩心的渗透率恢复率超过 90 % ,高于 3%MMH钻井液及加入屏蔽暂堵剂YFP的 3%MMH钻井液污染后岩心的渗透率恢复率。所开发的聚合醇钻井液已在胜利油田 80余口井钻井中使用 ,介绍了一口斜井。

我国天然高分子基钻井液体系研究进展

钻井液是油气勘探开发中首个与油气层相接触的外来流体,其体系和配方优选是钻井过程中油气层保护技术的核心内容之一。聚焦适用于复杂地层的环保天然高分子基钻井液体系,综述了近几年我国天然高分子基钻井液体系极具代表性的研究成果,并融入国内具有一定影响力的课题组在此领域取得的研究成果,分门别类地介绍了天然杂聚糖类、纤维素基、淀粉基、烷基糖苷类木质素基等天然高分子基钻井液体系,探讨了天然高分子基钻井液体系的热点问题,并对其应用方向及主要发展趋势进行了展望。

油田化学品在钻井中的应用及发展趋势

介绍了国内外钻井液、完井液、保护油气层等用油田化学品的研究及应用的现状 ;提出正电性钻井液体系是今后钻井液及完井液的发展方向 ;油田化学品的发展趋势是 :在油田化学新理论指导下 ,进行油田化学品分子设计、开发新型单体。

钾铵基聚磺钻井液体系在大牛地气田水平井钻井中的应用

大牛地气田水平井钻井中,由于A点前井眼尺寸较大,二叠系石千峰至下石盒子组泥岩普遍存在易水化膨胀、剥落、掉块、垮塌现象,处理复杂情况导致钻井周期长。经过2口水平井的钻井实践,摸索出了适合A点前的钾铵基聚磺钻井液体系,减少了井下复杂情况,提高了钻井效率,缩短了A点前的钻井周期,从而提高了该工区钻进水平井的综合效益。