An Experimental Investigation on the Chemical Stability of Selected Formation and Determination of the Proper Type of Water-Base Drilling Fluids. Part 2. Test Results

The objective of this study was to select the proper drilling fluid type and composition for drilling stable holes through the problems of the selected formations. This study was performed on shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. Both ionic and polymer inhibitions were utilized in formulating the proper drilling for the Germav formation. Ionic inhibition was obtained using KCl and NaCl. Polyanionic polymer (Pac-L) was used for providing the polymer encapsulation. Experimental results indicated that KCl is superior to NaCl in providing ionic inhibition. Both salts lowered the interaction between the drilling fluid and Germav formation, but better results were obtained with KCl. Minimum salt concentration up to 15% yields more inhibitive environment. Polymer inhibition tests indicated that minimum Pac-L concentration required for maintaining the polymer inhibition was about 2 lb/bbl for both systems. In conclusion, KCl/encapsulating polymer system seems to be the most proper water: base drilling fluid available for Germav formation achieving the required wellbore stability. The fluid loss and suspending properties of the proposed system must be controlled using the modified starch and XC polymer.     

Permeability Reduction Due to Formation Damage by Drilling Fluids

Abstract

In this study, investigation of permeability reduction due to formation damage by invaded drilling fluids of sandstone-based, lime-containing core plugs from the southeastern region of Turkey were studied. The tests were performed by using dynamic filtration set-up that was constructed at the laboratory. In the experiments, nine core plugs of 7 cm length and 3.81 cm (1.5 in) diameter were used. Three different drilling fluid types using two different polymers were prepared and tests were made at three different filtration pressures. The direct effect of filtration pressure on fines migration was studied. The filtration properties and the thicknesses of the filter cakes were measured. It was observed that permeability of the sandstone samples reduced due to circulation of the drilling fluid and the filter cake thickness increased with increasing differential well bore pressure.     

可循环微泡沫钻井液的性能评价与应用

可循环微泡沫钻井液是由水、固相颗粒(黏土)、表面活性剂(发泡剂)、增黏剂、降滤失剂等制成的一种气、液、固三相分散的胶体体系。室内评价实验结果表明,可循环微泡沫钻井液抗温高达135℃,在NaCl浓度高达10%时仍保持良好的流变性,具有较强的抑制性和良好的防漏失性能。由于其所含的表面活性剂产生泡沫,具有一定的疏水特性,在井内循环过程中,在井壁表面形成稳定的疏水屏障,阻碍自由水向地层的流动,使之不易润湿及渗入裸露的井壁,减少了滤液对泥页岩地层的水化膨胀作用;泡沫钻井液与抑制剂及井壁稳定剂适量添加混合,可有效提高钻井液的防塌效果。室内评价试验确定了可循环微泡沫钻井液使用配方:4%膨润土浆+0.3%Na2CO3+0.5%WP-1+0.3%WDJ-1+0.4%CPS-2000+0.3%FP-1。中原油田4口井和科索1井的现场应用表明,该钻井液可满足中原油田中生界低压、低渗地层和北京中元古界蓟县系雾迷山组海泡石易膨胀、溶解地层、气穴发育地层的欠平衡钻进要求。     

Effects of Polymers and CMC Concentration on Rheological and Fluid Loss Parameters of Water-Based Drilling Fluids

Abstract

Fluid loss during drilling operations has a very significant effect on both reservoir formation damage and monetary terms. There are many additives to control this unwanted phenomenon. Nevertheless, most of these substances are artificial chemicals. Thus, they are not only expensive, but also hazardous to the environment. In this article, a more natural method was applied to overcome the higher filtration problems by employing carboxyl methyl cellulose (CMC) and polymers (XT), DSHV, and MAC PR. Drilling fluids were prepared due to American Petroleum Institute (API) standards. The fluid weights were adjusted as 9 ppg. API filtration tests were applied to fluid samples including the chemicals. Tests were also conducted with non-treated bentonites + barite fluids without chemicals for comparative purposes. All of the rheological parameters including plastic and apparent viscosity and yield points were determined. Comparative graphs of shear stress vs. shear rates were plotted. The optimum CMC and polymer amounts were selected by graphical analysis of the results of rheological tests made by using shear meter and filtration tests. An optimization of the fluid loss control due to addition of the chemicals was made. The behavior of water-based fluids with CMC and polymers was examined. The accurate and sensitive industrial application of this study would reduce drilling fluid loss expenditures effectively.     

Effects of Walnut Shells on the Rheological Properties of Water-Based Drilling Fluids

Abstract

In this research, three different water-based drilling fluids were prepared according to American Petroleum Institute (API) standards, and effects of walnut shells on the rheological properties of the samples were studied. The walnut shells of 2-, 4-, and 6-mm samples and their equal weight mixtures of 2–4 mm and 4–6 mm were added to the drilling fluid samples in different concentrations. The aim of this study is to determine the optimum walnut shell size, concentration and polymer concentration to minimize the fluid loss during drilling operations. It was observed that polymer (XT) has the optimum effects on the water-based drilling fluid. The optimum concentration of polymer (XT) with the 6-mm walnut shell is determined as 0.4 g/350 ml.     

2009～2010年国内钻井液处理剂研究与应用进展

随着石油勘探开发向深部和海上发展,深井、超深井以及特殊工艺井钻探越来越多,特别是超高温、超高压地层的钻探,对钻井液提出了更高要求。针对钻井液技术发展的需要,促使油田化学工作者不断开发新型钻井液处理剂。近两年,国内在钻井液处理剂方面开展了一系列卓有成效的研究工作,其中一些研究已在现场应用中见到效果,部分产品已达到或超过世界先进水平,从而为钻井液技术的进步奠定了基础。从天然材料改性、合成材料、工业废料或副产物利用,以及不同材料复合或反应产物等方面,就2009～2010年国内钻井液处理剂研制及应用情况进行介绍,并指出处理剂的发展方向。从近期的研究看,仍然以合成聚合物为主,多围绕提高产品的抗温抗盐这一方向,并逐步向超高温发展,且研究最多的是钻井液降滤失剂,其次是降黏剂、堵漏剂和润滑剂等。而在钻井液降滤失剂、降黏剂中,又以2-丙烯酰胺基-2-甲基丙磺酸等含磺酸基单体与其他单体的共聚物更受重视,而润滑剂、堵漏剂等则多以多种材料复配为主。今后,在处理剂研究上,要强化基础研究和新原料的开发,发展低相对分子质量的聚合物处理剂,进一步加强淀粉、褐煤、栲胶、木质素等天然材料的深度改性,研制绿色、价廉的钻井液处理剂。     

关于加快发展我国油基钻井液体系的几点看法

油基钻井液具有抗高温、抗盐钙侵、有利于井壁稳定、润滑性好和对油气层损害程度小等优点.国外早在20世纪60年代,就十分重视油基钻井液技术的开发与应用,现已广泛作为钻深井、超深井、海上钻井、大斜度定向井、水平井和水敏性复杂地层及储层保护的重要手段.国外油基钻井液体系及配套技术比较成熟,国内在油基钻井液方面尽管开展了一些工作,但应用较少,还没有形成体系.目前,国内非常规油气资源的开发已经启动,对油基钻井液有了迫切需求.我国应在油基钻井液应用方面尽快行动起来,在借鉴国外经验和国内初步实践的基础上,首先开展油基钻井液的应用,在应用中积累经验、完善体系,并通过油基钻井液处理剂(降滤失剂、提黏切剂、封堵剂及润湿剂)的研制,逐渐形成具有国内特点,能够满足现场需要的油基钻井液体系,以及钻井液回收处理循环再利用的配套设备与方法.同时,开展油基钻井液高温下流变性、稳定性研究,以形成系统的流变性控制方法,为油基钻井液体系的应用提供理论支撑,促进国内页岩气等非常规油气资源的开发.     

关于规范钻井液处理剂及钻井液体系的认识

自上世纪70年代以来,我国钻井液技术逐步趋于成熟,与国外的差距日渐缩小。特别是近年来,围绕高温、高压地层以及强水敏地层、页岩气水平井的需要,在超高温钻井液、超高密度钻井液、页岩气水平井钻井液、油基钻井液等方面又有了新进展。但在钻井液处理剂和钻井液体系规范方面还存在问题,如在命名方面,钻井液处理剂任意编代号,随便起名字,钻井液体系缺乏主题和依据,有时仅仅加入了很小量的某种处理剂,就称"某钻井液体系";标准方面,因制定中缺乏实验和应用依据,多数行业标准系由企业标准转化而来,标准中缺少表征产品本质特征的项目及指标,通用性不强;加之高纯度、高质量产品推广受到价格限制,不同程度上制约了钻井液技术的发展。从钻井液处理剂和钻井液两方面提出规范思路。基于实验和分析认为,处理剂规范应从分类、命名、指标设置和实验方法等方面出发,以保证命名的科学性和标准的准确性与适用性。在钻井液体系方面,基于处理剂、标准、质量控制和钻井液性能间的关系,提出钻井液体系的命名原则,明确了钻井液技术规范、钻井液体系或工艺规范应包括的内容。     

Extensional Viscosity of Polymer Based Fluids as a Possible Cause of Internal Cake Formation

Abstract

In this study, the effect of the rheology of viscoelastic fluids on the formation of internal filter cakes has been investigated. A series of core flow experiments have been conducted to investigate the possible relationship among the polymer concentration, fluid extensional viscosity, shear viscosity, filtration loss characteristics, and pressure drop across the core samples, and hence, any change in the original rock permeability. Results of extensional and shear viscosity measurements, API filtration loss tests, and formation damage tests conducted by using three different partially hydrolyzed polyacrylamide (PHPA) solutions (0.5, 1.5, and 3.0 lb/bbl) are shown. Comparison of the PHPA test results with the previously published xanthan gum (XG) test results is also provided.     

胜利油区河50丛式井组调整井钻井技术

河50断块丛式井组为全国最大的陆基平台井组,1989年投入开发,共有油水井45口,其中斜井43口,最大井斜角在19°～63°之间,现已进入高含水期,产能建设亟需进行调整开发。该断块探明含油面积2.6km2,地质储量1052×104t,可采储量242×104t,呈扇状分布,属稀油低渗、低饱和高压岩性构造油藏,具有天然能量充足、产量递减快的特点。由于老区采油地层压力亏空,调整井钻井过程中易出现井漏、井涌、坍塌等复杂情况,加之老区井网密集、斜井众多,井身轨迹控制困难,防碰难度大,对钻井技术、油气层保护和固井质量提出了更高的要求。对此,制定了井身轨迹控制与防碰技术措施;优选了适宜不同地层的钻井液体系;形成了井壁稳定与承压堵漏技术、固井技术和油气层保护技术。实钻效果表明:河50丛式井组调整井钻井技术有效解决了该区块井漏、井塌、缩径及固井时水泥浆漏失等井下复杂情况,井身质量和固井质量合格率均为100%。     

河坝构造复杂工程地质问题与安全优快钻井技术对策

河坝构造钻井工程难度大,存在漏、塌、卡、涌、毒、硬、斜等问题,钻井效率低、周期长,需要在工程地质特征基础上,提高钻井工程工艺的针对性。本文在岩石力学实验基础上,建立工区岩石力学参数剖面,表明该构造地层岩石致密,抗压强度、抗剪切强度、硬度大,可钻性差。根据地层孔隙压力、坍塌压力、破裂压力剖面,开展井壁稳定性分析,表明该区纵向多压力系统,陆相地层坍塌压力高,易井壁失稳;海相地层异常高压,安全钻井液密度窗口窄,井壁力学稳定性差。结合工程地质特征,提出优化井身结构设计,优选气体钻井、泡沫钻井、垂直钻井、复合钻井、旋转导向钻井等钻井技术,优选钻头型号,优选钻井液,优选防漏堵漏技术等钻井对策。现场实钻证实,上述对策大幅提高了机械钻速,有效减少了钻井复杂情况,大幅缩短了钻井周期,实现了河坝构造海相超深气井优快钻井。     

胜利油田博24区块水平井筛管外泥饼酸洗工艺应用

胜利油区博24区块水平井采用常规酸洗工艺时,存在成功率低、酸洗效果差的问题,主要表现为:①未考虑酸液与混油聚合物钻井液、污水以及地层的配伍性,酸洗效果差;②酸洗工艺中,未能对酸液使用量、注入与替出排量、反应时间等进行优化设计,致使酸液对近井地带的清洗效果欠佳;③酸洗泥饼时,一处的污染解除,酸液由此渗入地层,导致其余井段无法有效清除污染物。为此,开展酸液与聚合物钻井液、与过滤污水、与地层的配伍性室内实验,最终确定了酸液配方,完善了酸洗工艺,实施了多级控压泥饼清洗工艺,对酸洗程序与解堵液用量进行优化。对该区块6口水平井的现场应用表明,改进后的二次酸洗工艺可减小泥浆污染,恢复或提升油层渗流能力;多级控压、段塞顶替,增加下铣锥及通井刮管作业程序,可以提高水平井筛管外泥饼酸洗工艺成功率与应用效果。6口水平井平均日产油7.82t/d,平均日产液15.9t/d,改进后的酸洗施工成功率高达100%。     

川西马井气田钻井复杂情况及治理对策

马井气田探明地质储量175.58×10^8m^3,可采储量80.54×10^8m^3,是川西地区主要的天然气开发区域。该区地质构造复杂,主要表现为成岩作用差,层间缝发育,层系间不整合接触,断层发育,地层承压能力差;纵向上泥岩较发育,各组岩性疏松,胶结差,钻井施工中复杂情况发生率较高,为73.7%（统计57口已完钻井）,其中,井漏占65%,卡钻占17%,井喷、井涌占9%,井壁垮塌占5%,地层出水占4%,从而导致钻井速度缓慢、施工周期延长。对此,提出如下治理对策：采用新的钻井工艺,引进清水强钻和微泡沫钻井技术;钻井中使用强抑制性高钙盐聚合物钻井液,并合理调整其密度大小;调整井身结构,在一个裸眼井段内不能有压力悬殊的地层存在,在揭开储层前,应适当提高钻井液密度。同时,应加强对该区地层出水原因及治理方法的研究工作。     

Analysis of reservoir pressure and decline curves in Serrazzano zone, Larderello geothermal field

An estimate of reserves in the Serrazzano reservoir was obtained from mass balance studies and production decline curve analyses.The Serrazzano reservoir consists of a geometrically well-defined structural high of permeable formations separated from the other productive regions of the Larderello field.Deep drilling began in the 1930s and was limited to a small area exhibiting natural manifestations. After the second World War the area of drilling was extended to about 20 km². Currently the drilling area is about the same. Even though the reservoir has been producing steam since the 1930s, a systematic collection of production data did not begin until after 1953.Data on average reservoir pressures were not available for the material balance calculations made in the study reported here. Calculated bottom hole pressures of shut-in wells were taken therefore to represent local static reservoir pressures. These pressures were used to calculate an “average reservoir pressure” which was graphed as a function of cumulative production. The reservoir pressure history corresponding to the first half of current cumulative production is not known. Data for the second half indicate a linear relationship between “reservoir pressure” and cumulative production.The conventional straight-line p/z vs cumulative production material balance relationship is known to be correct, of course, for closed single-phase gas reservoirs. The validity of this linearity for stream-producing systems with boiling water has not been proved. Regardless of this, the following observations were made: a line connecting the available data points extrapolated back to zero production indicates an initial reservoir pressure approximating at least 40 atm. Extrapolating the same data to zero reservoir pressure indicates the total initial steam in place to be about 170 × 10⁶ tons.An empirical type-curve matching technique was applied to the production decline curves of wells in the reservoir. The curve for each well was extrapolated to infinite production time to obtain an estimate of total past and future production. Summing these values for all producing wells in the reservoir, an estimated total production (past and future) of 200 × 10⁶ tons was obtained.The agreement between the estimated total production applying material balance principles and decline curve analyses is remarkably good. Although these results may be useful, further field and theoretical work are necessary to prove their validity.     

应用水平井挖掘杜84块兴Ⅱ组单砂体稠油油藏潜力

辽河油田杜84块兴隆台油藏纵向划分为兴Ⅵ组、兴Ⅲ组、兴Ⅱ组、兴Ⅰ组四套油层组。其中,兴Ⅵ组采用直平组合SAGD(蒸汽辅助重力泄油技术),兴Ⅰ组采用双水平井SAGD,兴Ⅱ、Ⅲ组互层状油藏水平井吞吐挖潜,实现杜84块多元化立体高效开发。通过开发方式转换,杜84块实现了油田纵向储量的均匀动用,很多区域达到或超过油田标定采收率(29.2%)。通过深化地质研究,发现兴Ⅱ组还存在未得到有效动用的单砂体油藏。结合部署界限和油藏发育情况,在兴Ⅱ组隔夹层发育稳定区域部署规划两口水平井杜84兴H2111井、杜84兴H2112井,控制地质储量11.5×104t,部署区域基本未动用。两口水平井目的层厚度在7m左右,水平段长度为240m以上,单井储量在5×104t左右。应用近钻头地质导向、随钻地质跟踪以及水平井同注同采技术,挖潜单砂体油藏潜力。     

油包水钻井液研究与应用

与水基钻井液相比,由于油基钻井液具有抗高温、抗盐钙侵、有利于井壁稳定、润滑性好和保护油气层等优点,成为钻遇深井、大斜度定向井、水平井和各种复杂地层的首选体系。油包水钻井液具有油基钻井液的优点。针对非常规油气藏及强水敏、易坍塌地层钻井的需要,研制了油包水钻井液,优化了钻井液配方:基液(油水体积比为8∶2)+3%主乳化剂+3%辅乳化剂+3%有机土+4%降滤失剂+3%的CaO+重晶石。室内评价结果表明,该油包水钻井液具有良好的流变性、悬浮稳定性、润滑性、乳液稳定性和抗污染能力。同时,完善了现场施工工艺,并在中原、新疆、西南等现场应用了7口井。应用证明,油包水钻井液稳定性好,破乳电压大于600V,抗污染、抗温能力强,遭受20%的水和岩屑污染后,钻井液性能稳定,易于维护处理;且钻井过程中井壁稳定,定向施工顺利,减少井下复杂,平均井径扩大率小于5%。该钻井液配制工艺简单,可以回收利用,满足页岩气水平井、易塌地层钻进的需要。     

我国深井钻井技术发展的难点及对策

分析了目前我国深井钻井技术面临的主要难点:井段内存在多套压力体系,喷漏共存;钻遇地层复杂,井壁稳定性差,井漏、井涌、井塌、缩径、卡钻等井下复杂情况频发;机械钻速低,钻井周期长,钻具易损坏;在地层倾角大的地区直井防斜难度大;深井井下温度高、压力大,钻井液、井下工具和测量仪器性能要求高;固井施工难度大。展望了深井钻井技术的发展趋势,并结合国内外钻井技术发展的最新进展,提出了加快我国深井钻井技术发展的对策:应用套管钻井技术、膨胀管技术,改善井身结构提高整体钻井速度;提高钻压、转数,增加钻头的切削能力和寿命,提高深部井段机械钻速;最大限度地扩大气体钻井的使用范围;增强地层承压能力,实现井壁稳定;降低固井施工难度,提高封固质量;提高工程事故的预防与快速处理能力。     

页岩气水平井钻井液技术的难点及选用原则

我国页岩气资源勘探开发已全面铺开。针对页岩气的成藏特征,页岩气开发以浅层大位移井、丛式水平井布井为主。由于页岩地层裂缝发育、水敏性强,长水平段钻井中不仅易发生井漏、垮塌、缩径等问题,且由于水平段较长,还会带来摩阻、携岩及地层污染问题,从而增大了产生井下复杂情况的几率。解决井壁稳定、降阻减摩和岩屑床清除等问题是目前页岩气水平井钻井液选择和设计的关键。选择页岩气水平井钻井液的原则是确保井壁稳定、润滑、防卡和井眼清洗。油基钻井液可提高水润湿性页岩的毛细管压力,防止钻井液对页岩的侵入,从而有效保持井壁稳定,同时还具有良好的润滑、防卡和降阻作用,是国内外目前采用最多的钻井液体系。当采用水基钻井液的时,利用低活性高矿化度聚合物钻井液或CaCl2钻井液以降低页岩和钻井液相互作用的总压力;采用浓甲酸钾、Al3+盐,可以通过脱水、孔隙压力降低和影响近井壁区域化学变化的协同作用产生良好的井眼稳定作用;对于有裂隙、裂缝或层理发育的高渗透性页岩应使用有效的封堵剂进行封堵;但对于强水敏性页岩地层,水基钻井液在抑制性方面仍然存在局限性。从环境保护的角度出发,甲基葡糖苷钻井液在井壁稳定机理方面与油基钻井液相似,未来可望作为有效的钻井液体系之一。随着以页岩气为代表的非常规油气资源的不断开发,为了满足安全钻井和环境保护的需要,未来页岩气水平井钻井液技术的研究应围绕高效、低成本水基钻井液和低毒油基钻井液来展开。     

含CaCl2的深水油基钻井液中甲烷水合物的生成规律研究

深水钻井常采用含有CaCl₂的油基钻井液,施工时气体侵入钻井液可能会导致水合物的生成,增加钻井风险。因此,明确钻井液中水合物的生成规律对水合物的防治工作具有指导意义。采用高压水合物搅拌釜,实验研究了含水率为10%、20%、40%的油基钻井液分别在273.15 K、275.15 K、278.15 K和CaCl₂质量浓度为3.5%、10%条件下的水合物生成规律,分析了水合物生成过程中钻井液的相对电流变化。实验结果表明,油基钻井液中水合物的生成可分为诱导、快速生成和缓慢生成三个阶段,在快速生成阶段,温度和盐度对水合物生成速率影响较小,随含水率增大,水合物生成速率增大;低含水率（10%、20%）时,水合物生成时钻井液的相对电流几乎不增大;高含水率（40%）且水合物体积分数小于15%时,钻井液的相对电流增大不明显,水合物体积分数为15% ~ 28%时,钻井液的相对电流随水合物体积分数的增大而增大,增幅为10% ~ 50%。