Rheological property of low-damage,ideal packing,film-forming amphoteric/sulfonation polymer drilling fluids

Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.

Experimental study of low-damage drilling fluid to minimize waterblocking of low-permeability gas reservoirs

This paper discusses the systematic design and development of low-damage drilling fluid to protect the low-permeability gas reservoir of the Sulige block in the Ordos Basin, Inner Mongolia Autonomous Region, China. Based on investigation of the geological characteristics and the potential formation damage of the Permian formation of the reservoir, waterblocking due to invasion of drilling or completion fluids was identified one of the most severe causes of damage to gas well deliverability. By adopting the phase trap prevention method, ideal packing theory, and film-forming technology, a lowdamage drilling fluid, sodium formate brine containing efficient waterblocking preventing surfactants, optimized temporary bridging agents （TBAs）, and film-forming agents has been developed. The performance of the new drilling fluid was evaluated by using a variety of techniques. The results show that the fluid has good rheological properties, good strong shale-swelling inhibition, good temporary plugging effect, ultra-low filtration, and good lubricity. It can efficiently minimize waterblocking and can be used to drill horizontal wells with minimal intervention of the reservoir in the Sulige Gas Field.

Development of Film Forming Agent HN-1 and Its Application in Drilling Fluid

Borehole instability and reservoir damage had become the international technical problems of petroleum exploration and development of complicated area, and the water of drilling fluid invading borehole wall and petroleum reservoir was the main cause of borehole instability and reservoir damage. In order to prevent the water of drilling fluid invading borehole wall and petroleum reservoir, domestic and foreign scholars recently put forward the technology of ultra-low permeable drilling fluid. Film forming agent was the key treating agent of ultra-low permeable drilling fluid, the film forming agent (HN-1) was developed, which did not affect properties of the drilling fluid and could decrease the filter loss of drilling fluid applied in Enping 24-2 oil field. Based on this research, ultra-low permeable drilling fluid could be applied to Enping 24-2 oil field. By the methods of testing ultra-low permeable drilling fluid properties, the drilling fluid invasion sand-bed depth, drilling fluid high temperature/high pressure (HTHP) sand-bed filter loss, the pressure-bearing ability of rock core and the ability of reservoir protection were studied. By synergistic effect, HN-1 containing the organic silicate and natural fiber polymer modified by organic amine prevented the liquid and solids in drilling fluid invading reservoir, decreased drilling fluid invasion sand-bed depth and drilling fluid HTHP sand-bed filter loss, improved the pressure-bearing ability of rock core and the ability of reservoir protection. The drilling fluid could decrease reservoir damage to the maximal degree, and it offered efficiency guarantee for exploitation Enping 24-2 oil field.

Characterization and prevention of formation damage for fractured carbonate reservoir formations with low permeability

Stress sensitivity and water blocking in fractured carbonate reservoir formations with low permeability were determined as the main potential damage mechanisms during drilling and completion operations in the ancient buried hill Ordovician reservoirs in the Tarim Basin. Geological structure, lithology, porosity, permeability and mineral components all affect the potential for formation damage. The experimental results showed that the permeability loss was 83.8%-98.6% caused by stress sensitivity, and was 27.9%-48.1% caused by water blocking. Based on the experimental results, several main conclusions concerning stress sensitivity can be drawn as follows： the lower the core permeability and the smaller the core fracture width, the higher the stress sensitivity. Also, stress sensitivity results in lag effect for both permeability recovery and fracture closure. Aimed at the mechanisms of formation damage, a modified low-damage mixed metal hydroxide （MMH） drilling fluid system was developed, which was mainly composed of low-fluorescence shale control agent, filtration control agent, lowfluorescence lubricant and surfactant. The results of experimental evaluation and field test showed that the newly-developed drilling fluid and engineering techniques provided could dramatically increase the return permeability （over 85%） of core samples. This drilling fluid had such advantages as good rheological and lubricating properties, high temperature stability, and low filtration rate （API filtration less than 5 ml after aging at 120 ℃ for 4 hours）. Therefore, fractured carbonate formations with low permeability could be protected effectively when drilling with the newly-developed drilling fluid. Meanwhile, field test showed that both penetration rate and bore stability were improved and the soaking time of the drilling fluid with formation was sharply shortened, indicating that the modified MMH drilling fluid could meet the requirements of drilling engineering and geology.

水基钻井液复合纳米成膜封堵剂的制备及性能

以改性纳米SiO_(2)为刚性粒子,丙烯酰胺、2-丙烯酰胺基-2-甲基丙磺酸、苯乙烯和醋酸乙烯酯为聚合单体,壬基酚聚氧乙烯醚(10)和十二烷基磺酸钠为乳化剂,过硫酸铵和亚硫酸氢钠为引发剂,合成了一种有机/无机复合纳米成膜封堵剂。采用FTIR、SEM、动态光散射(DLS)和TGA对产物进行了表征和测试。考察了不同质量分数复合纳米成膜封堵剂对水基钻井液的流变性、滤失性及封堵性能的影响。结果表明,复合纳米成膜封堵剂呈球形,并保持纳米级分布,中值粒径为325 nm;340℃时的质量损失率为14%;120℃、16 h老化后较老化前表观黏度和塑性黏度均明显增加。当复合纳米成膜封堵剂质量分数为3%时,水基钻井液的静滤失量为10 mL;当质量分数≥2%后,砂床滤失量为0;当质量分数从0增至4%时,高温高压滤失量从104 mL减至29 mL,渗透性为1.56×10^(–2)mD,封堵率为90.7%。

低孔低渗砂岩储层废弃钻井液环境污染土壤深度研究

在油气田勘探开采过程中,废弃钻井液的泄露会污染油气田生态环境,造成土壤的理化性质改变、植物枯萎等现象,为便于控制污染,提出低孔低渗砂岩储层废弃钻井液环境污染土壤深度研究。分析储层废弃钻井液环境污染特性,根据废弃钻井液滤失量与时间的关系构建废弃钻井液滤失量计算模型,构造废弃钻井液污染土壤深度估算公式,实现了储层废弃钻井液环境污染土壤深度的分析。实验数据显示:在不同实验工况背景下,应用提出方法获得的废弃钻井液污染土壤深度估算误差最小值为2%,充分证实了提出方法应用性能佳。

新型纳米胶乳封堵剂在陆丰区块的应用

为解决传统堵剂封堵低渗透泥页岩地层的难题,开发了一种新型球形核壳纳米胶乳PF-NSEAL,并对其压力传递和微孔封堵性能进行了评价。压力传递和微孔封堵实验表明,纳米胶乳堵漏剂有效降低了钻井液的页岩孔隙压力传递率,改善了微孔封堵性能。随后,PF-NSEAL成功应用于陆丰区块古近系地层。现场聚合物KCl钻井液中加入PF-NSEAL后,页岩封堵效果增强,滤失量明显降低,井壁失稳现象明显改善。这为未来的大规模应用提供了重要的现场操作参考。

复合盐成膜钻井液技术研究

为解决松辽盆地长岭断陷长裸眼硬脆性泥页岩井段的塌漏失共存的技术难题,在优选活度调节剂和成膜封堵防塌剂的基础上,研制了复合盐成膜防塌钻井液体系。该体系流变性能可控,滤失造壁性能佳,抑制和防塌性能优异。在腰登15HF井的现场应用中,成功解决了长裸眼硬脆性泥页岩井段的塌漏失共存的问题,起下钻、电测和下套管作业无遇阻,推广前景广阔。

广西苗儿山大厚度水敏性地层冲洗液技术研究及应用

广西苗儿山地区铀矿找矿潜力巨大,但局部地区地层复杂,存在大厚度水敏性地层及破碎地层,钻探施工中频繁遇到孔壁坍塌及钻孔超径等难题,导致孔内事故频发,严重影响施工进度。因此,对该地区水敏性岩心进行了矿物成分和微观特征分析,分析结果表明水敏性地层含有大量蒙脱石、高岭石、水云母等粘土矿物,且微裂隙发育,水化膨胀严重。针对以上问题,通过室内实验评价,优选了新型成膜护壁材料,进一步研制了护壁性良好的成膜护壁冲洗液体系,其最优配方为:5%成膜A剂+3%成膜B剂+1.5%改性沥青+1%随钻堵漏剂+1%封堵剂+0.6%增粘剂+0.2%包被剂。该冲洗液API滤失量为5~8 mL,相对膨胀降低率达到87%以上,可有效抑制水敏性岩心水化膨胀,护壁效果明显。该技术在苗儿山地区3个试验钻孔成功应用,顺利钻穿水敏性地层,未发生岩心分散、孔壁坍塌等问题,取得了良好的应用效果,初步形成了针对该地区水敏性地层的成膜护壁冲洗液技术。

柳州地区页岩气地质调查井钻探技术研究与应用

页岩气地层裂隙发育,胶结性差,表现为岩石破碎、水敏性强、孔壁强度低。在钻进过程中容易出现坍塌、掉块、缩径等复杂情况,从而引发孔壁失稳、卡钻、埋钻等孔内事故。对广西柳州地区页岩气地质调查井工程进行钻探技术研究,应用PVA1788成膜体系无固相冲洗液和成膜防塌体系无固相冲洗液、绳索取心液动锤钻进技术、膨胀波纹管护壁新技术、螺杆钻具定向钻进纠斜技术,在现场勘探施工中取得了良好的效果,保证了项目的顺利施工。

小井眼高性能水基钻井液的研制和应用

针对江苏油田“低渗、低产”油气藏钻井投资高的问题,小井眼钻井可节约投资,但其对钻井液性能要求高。通过对水基钻井液核心处理剂优选,研制出一种适合小井眼钻探要求的高性能水基钻井液体系,并对其综合性能进行了评价。结果表明:该体系配方悬浮携岩性能强、润滑性优良,润滑系数仅0.078,防塌抑制性强,页岩膨胀率<20%,储层保护效果好,渗透率恢复值>78%。经现场应用证明,该体系易转化维护,定向段携岩好,返出岩屑颗粒较大、完整度好,钻进中无垮塌掉块,机械钻速高,符合小井眼钻井液性能要求。本研究成果可为东部油田低成本的小井眼钻井提供钻井液技术支持。

唐东探评井成膜封堵储层保护技术

大港油田唐东区块地层复杂,主要目的层为东三段和沙河街组,目的层埋藏较深、储层段长,且各储层之间损害机理差异性大,应用细目碳酸钙和钻井液用封堵剂作为储层保护技术,由于储层针对性不足且技术实施管理不到位,导致该地区探评井储层保护效果欠佳,储层钻井液岩心渗透率恢复值仅为67.5%。根据唐东9X6井岩心敏感性评价和铸体薄片分析,针对潜在损害因素构建了唐东探评井钻井过程储层保护技术体系。该保护体系采用成膜封堵保护技术,配合应用单井多层/多点设计方法,通过精细技术实施管理、精益实时评价,确保了技术高效实施。该地区成膜封堵保护技术实施5口井,钻井液动态滤失量降低25.7%、渗透率恢复值提高13.1%,5口井均达到地质预期效果,其中2口井实现高产,初期日产分别达到61.3 t和101.1 t,取得了良好的效果。

湘南3000 m科学深钻孔内事故处理及对策

湘南3000 m科学深钻为湖南首个3000 m地质岩心钻探特深孔,位于复杂褶皱转折带,钻遇了粘土缩径、全孔漏失、水敏性坍塌缩径和垂直节理发育坍塌等多种复杂地层,发生多次孔内事故。针对卡钻和塌孔等主要孔内事故,优化钻孔结构、冲洗液体系和钻具组合,采用侧钻绕障、循环捞砂、成膜冲洗液护壁和水泥浆护壁等多种技术措施,有效应对施工中的各种难题。终孔孔深3008.93 m,平均岩心采取率98.16%,实现了预期目标,为该区深部矿产成矿理论研究及资源勘查,提供了合格的地质钻孔和实物岩心资料。

页岩微纳米孔缝封堵评价方法研究

针对微纳米级孔缝的超低孔超低渗页岩地层,国内外缺少可靠的方法对其封堵进行评价。实验以延长组长7段页岩为参考对象,测试了页岩的岩性、孔隙特征等数据;通过研究膨润土、各类钻井液处理剂和API重晶石对泥饼厚度及渗透率的影响,构建了模拟页岩的“标准厚泥饼”封堵评价方法,厚泥饼平均厚度为10.05mm、平均渗透率为4.81×10^(-4)mD,且具有良好的重现性,能定量评价微纳米封堵剂SPA-1在甲酸钾钻井液体系中的封堵效果,解决了页岩封堵剂及水基钻井液封堵效果评价难题,对保障页岩井壁稳定具有指导意义。

磷石膏地层用钙基成膜环保冲洗液研究与应用

针对磷石膏地层水平孔钻探工程存在松散磷石膏层孔壁坍塌、磷石膏遇水分散影响取心质量、冲洗液受钙侵导致其性能恶化以及钻孔轨迹控制困难等技术难题,同时满足绳索取心钻进工艺要求,室内针对性地开展了冲洗液技术研究,分析了磷石膏地层水平孔钻进对冲洗液性能的要求,并在室内处理剂优选、配方优化的基础上,研发了钙基成膜环保冲洗液体系,并成功应用于贵州某磷石膏矿尾矿库中的水平孔钻探工程。室内试验及现场应用结果表明,该体系具有良好的抗钙侵能力,滤失量低,流变性能相对稳定;能够在岩心表面形成相对坚固的保护膜,强化磷石膏孔壁,有效预防孔壁坍塌;保护岩心免受冲洗液侵蚀,提高了取心质量。此外,该体系由无毒和易降解的环保材料组成,具有良好的环保性能。

白银市土红湾-李家沟煤炭资源详查23-2 孔冲洗液技术

甘肃省白银市土红湾-李家沟煤炭资源详查23-2孔地质条件极其复杂,既有水敏性强的泥岩,还有松散破碎的煤层等,其间还夹杂着不同程度的盐膏,孔内容易出现坍塌、掉块等问题,冲洗液易受到污染,对冲洗液性能提出了更高的要求。以往该矿区施工,常发生孔壁坍塌、冲洗液粘度显著降低等问题,严重时导致埋钻及沉砂卡钻等孔内事故,影响成孔和施工效率。针对以上问题,分析了钻遇地层孔壁失稳的原因,评价了盐膏侵对冲洗液性能的影响,并有针对性的开展了体系的适应性研究,先后优选出成膜防塌冲洗液和抗盐膏侵成膜环保冲洗液。施工中,针对水敏性分散剥落地层和松散地层选用成膜防塌无固相冲洗液,在发现盐膏侵后将其转化为抗盐膏侵成膜环保冲洗液,并通过对冲洗液配方、性能参数的合理调整与维护以及采用绳索取心钻探等工艺措施,较好地解决了上述问题。

低压低渗透气田Ø139.7 mm套管开窗侧钻水平井钻井液技术

苏里格气田属于低压低渗透气田,部分常规井已失去开采价值,实施Ø139.7 mm套管开窗侧钻水平井有助于老井恢复新的采气能力,与常规井眼相比,Ø139.7 mm套管开窗侧钻水平井井眼存在润滑防卡、水平段泥岩坍塌、窄环空间隙易漏失等技术难点。研制了强抑制、强封堵CQSP-4钻井液体系,并对其流变性、防塌性、抑制性、润滑性进行了室内评价,实验表明,100℃、12h岩屑滚动回收率达95.63%,100℃热滚24 h后API滤失量2.8 mL、高温高压滤失量13.2 mL,抗钻屑污染能力高达14%。对开窗侧钻、裸眼段钻进、钻井液固相控制、防漏、降摩减阻、井眼清洁等钻井液工艺进行了优化,截至2022年12月共进行了18口井现场应用,钻井周期较2017-2018年降低69.58%,机械钻速提高了102.82%,平均钻井周期由之前的80.5 d降至24.49 d,达到了提速提效的目的。该技术可为国内其他地区同类井施工提供借鉴。

松辽盆地北部地区小口径油气钻井施工技术

为了探查松辽盆地北部地区的地层情况,评价预测石炭—二叠系的油气前景,我队在该地区参与实施了4口油气地质调查井,设计井深均为2000 m。我队运用小口径绳索取心钻进工艺进行全孔取心,在取心率和取心质量等技术指标上都圆满完成了设计要求。由于松辽盆地北部地区为盆地沉积地层,地层情况复杂,大部分为泥岩、砂岩地层,易水化,发生坍塌、掉块、缩径等复杂井内事故,影响钻井事故进度和取心质量。为保证钻井的顺利实施,我队在钻进过程中,根据钻进地层情况,进一步优化钻具组合和钻进参数,选择护壁性能强的成膜防塌冲洗液体系,圆满完成了钻井施工任务,取得了较好的钻探成果。

钻井液隔离膜理论与成膜钻井液研究

特殊的水溶性聚合物在井壁岩石上吸附形成的膜具有防塌和储层保护作用。应用浓差极化理论对聚合物半透膜的“过滤”过程进行了分析,阐述了“隔离膜”的概念以及从半透膜到隔离膜的转变原理。隔离膜的概念可以认为是由于浓差极化产生的二次膜或者三次膜甚至多次膜的作用,使钻井液中的自由水在膜上的渗透率大为降低甚至为零,最终表现为没有滤失量的增加,因此隔离膜是在半透膜形成的基础上经过多次物质的沉积“污染”而形成的。采用滤失实验、透水实验和改性膨胀实验,利用研制出的多糖类聚合物进行了成膜实验研究。Plj成膜剂以植物天然分泌物为原料,改性加工后的天然分泌物分子量为8.4×105,分子长度为4500nm,分子直径为19nm,该剂经酸水解后是一种无色无味可食的天然大分子,其中一部分为含有plj酸的高聚物,易溶于水形成真溶液,而另一部分为以半乳糖残基为主键、阿拉伯糖残基为支键的中性多糖,易吸水溶胀成凝胶状物质。膜的承压实验、透水实验、半透性实验、动滤失实验结果证明,该聚合物具有良好的成膜效果,并且通过应用研究出的LG-1膜清除液对膜的清除效果很好。

成膜封堵低侵入保护油层钻井液技术的研讨

为使钻井过程所采用的钻井液对所钻遇的不同渗透率油层均能有效地阻止其固相与液相进入油气层,不诱发储层的潜在损害因素,防止对储层发生损害,提出了成膜封堵低侵入保护油气层钻井液技术的新构思。其核心是在钻开油气层钻井液中加入成膜剂、特种封堵剂和降滤失剂。在钻开油气层的极短时间内,此钻井液中的膨润土、加重剂、岩屑等固相在不同渗透率的油层表面架桥、填充形成内外泥饼,特种封堵剂和高温高压降滤失剂封堵近井壁油层内外泥饼的孔喉,成膜剂在井壁上成膜,封堵孔喉未被架桥粒子、填充粒子、降滤失剂封堵的空间,从而形成钻井液动滤失速率为零、厚度小于1 cm的成膜封堵环带,有效阻止钻井液固相和液相进入油气层。此项技术对钻遇的不同渗透率油层均能有效减少损害,通过室内实验证实了其可行性。