Preparation and properties of magnesium oxysulfate cement and its application as lost circulation materials

Loss of drilling fluids in large porous and fractured zones inevitably up-regulates the overall cost of drilling.As a type of acid-soluble cement,magnesium oxysulfate(MOS)cement is arousing huge attention for the less hygroscopic nature and less damaging to steel casings compared with magnesium oxychloride(MOC)cement.The present study developed MOS cement as a fast setting,high strength and acid-soluble lost circulation material to reduce the problem of losses.As suggested in this study,a higher strength of MOS cement at 70℃could be achieved by elevating M_(g)O/MgSO_(4)·7 H_(2)O molar ratio or downregulating H_(2)O/MgSO_(4)·7 H_(2)O molar ratio.Boric acid and borax could act as effective retarders.Plugging slurry based on MOS cement could effectively block the simulated porous loss zones exhibiting a diameter from 1.24 mm to 1.55 mm,as well as the fractured loss zones with a width from 2 mm to 5 mm and bearing a pressure difference up to 8 MPa.Permeability recovery test demonstrated that it facilitated future oil and gas production.The successful field application in the Junggar Basin,Xinjiang,China verified the significant plugging effect of MOS cement for severe loss problems.

Bridging performance of new eco-friendly lost circulation materials

Lost circulation is one of the most important concerns of the drilling industry, causing excessive expenditure and increasing the non-productive drilling time. In this study, various lost circulation materials(LCMs) were used to control the lost circulation of two types of drilling fluids, bentonite mud and a new eco-friendly mud, named RIA-X, which has a remarkable effect on decreasing the amount of lost circulation in fractured and highly permeable reservoirs. The Bridging Material Test(BMT) apparatus was used to investigate the effectiveness of various LCMs in fractures of various sizes and to select the LCM and combination with the best performance. The use of three-dimensional fractures is one of the most notable points of this work, which makes the experimental conditions similar to those of real wells. The lost control performance of the new eco-friendly LCMs in RIA-X mud was tested in field. The outcomes show that the designed LCMs are able to control severe lost circulation that regular processes such as cementing or drilling with foam cannot deal with.

Lost circulation material for abnormally high temperature and pressure fractured-vuggy carbonate reservoirs in Tazhong block, Tarim Basin, NW China

To effectively solve the problem of lost circulation and well kick frequently occurring during the drilling of abnormally high temperature and pressure fractured-vuggy reservoirs in the Tazhong block, a rigid particle material, GZD, with high temperature tolerance, high rigidity(> 8 MPa) and low abrasiveness has been selected based on geological characteristics of the theft zones in the reservoirs. Through static pressure sealing experiments, its dosage when used alone and when used in combination with lignin fiber, elastic material SQD-98 and calcium carbonate were optimized, and the formula of a new type(SXM-I) of compound lost circulation material with high temperature tolerance and high strength was formed. Its performance was evaluated by compatibility test, static sealing experiment and sand bed plugging experiment. The test results show that it has good compatibility with drilling fluid used commonly and is able to plug fractures and vugs, the sealed fractures are able to withstand the static pressure of more than 9 MPa and the cumulative leakage is 13.4 mL. The mud filtrate invasion depth is only 2.5 cm in 30 min when the sand bed is made of particles with sizes between 10 mesh and 20 mesh. Overall, with good sealing property and high temperature and high pressure tolerance, the lost circulation material provides strong technical support for the safety drilling in the block.

Study on an novel composite gel material solving serious lost circulations and pressurization sealing

Lost circulations have presented great challenges to the petroleum industry, causing great expenditures of cash and time to fighting the problem. Probably the most problematic situations are the naturally fractured formations where the operator may face total loss with no mud return in the annular. The voids or large fracture encountered in this case are often far too large to be plugged with conventional Lost Circulation Material. This paper will give a detailed introduction on a novel composite gel material usable to control severe losses and pressurization sealing. The plugging mechanics of this new composite gel material, which is different from conventional lost circulation materials, were elaborated as well. In addition, the properties of the new composite gel material such as thermostability, sealing strength and bearing resistance are characterized with specific experimental devices. The experimental results proved that the breakdown pressure of the new plugging reached more than 20MPa, and the maximum degraded temperature can be exceed 130℃. The field application at 4 wells in Puguang gas field, SINOPEC, demonstrated that the new composite gel material solved the serious loss in Ordovician carbonate fractured formation successfully and guaranteed the following completion cement operation smoothly. The composite gel sealing slurries, which was easily prepared on site, gives remarkable properties regarding pumping through drill pipes, adjustment of setting time and excellent sealing strength of the lost zone sealing, additionally, the whole pressurization sealing process was complicated within only ten hours. The on-site results show that the plugging ratio of the new composite gel was reached 100%, and the success rate of sealing operation kept above 80%.Thus the new LCM can guarantee safe drilling jobs and save operation cost more effectively.

Research progress and prospect of plugging technologies for fractured formation with severe lost circulation

By reviewing the mechanisms of drilling fluid lost circulation and its control in fractured formations, the applicability and working mechanisms of different kinds of lost circulation materials in plugging fractured formations have been summarized. Meanwhile, based on the types of lost circulation materials, the advantages, disadvantages, and application effects of corresponding plugging technologies have been analyzed to sort out the key problems existing in the current lost circulation control technologies. On this basis, the development direction of plugging technology for severe loss have been pointed out. It is suggested that that the lost circulation control technology should combine different disciplines such as geology, engineering and materials to realize integration, intelligence and systematization in the future. Five research aspects should be focused on:(1) the study on mechanisms of drilling fluid lost circulation and its control to provide basis for scientific selection of lost circulation material formulas, control methods and processes;(2) the research and development of self-adaptive lost circulation materials to improve the matching relationship between lost control materials and fracture scales;(3) the research and development of lost circulation materials with strong retention and strong filling in three-dimensional fracture space, to enhance the retention and filling capacities of materials in fractures and improve the lost circulation control effect;(4) the research and development of lost circulation materials with high temperature tolerance, to ensure the long-term plugging effect of deep high-temperature formations;(5) the study on digital and intelligent lost circulation control technology, to promote the development of lost circulation control technology to digital and intelligent direction.

Structural failure mechanism and strengthening method of fracture plugging zone for lost circulation control in deep naturally fractured reservoirs

Focused on the lost circulation control in deep naturally fractured reservoirs, the multiscale structure of fracture plugging zone is proposed based on the theory of granular matter mechanics, and the structural failure pattern of plugging zone is developed to reveal the plugging zone failure mechanisms in deep, high temperature, high pressure, and high in-situ stress environment. Based on the fracture plugging zone strength model, key performance parameters are determined for the optimal selection of loss control material(LCM). Laboratory fracture plugging experiments with new LCM are carried out to evaluate the effect of the key performance parameters of LCM on fracture plugging quality. LCM selection strategy for fractured reservoirs is developed. The results show that the force chain formed by LCMs determines the pressure stabilization of macro-scale fracture plugging zone. Friction failure and shear failure are the two major failure patterns of fracture plugging zone. The strength of force chain depends on the performance of micro-scale LCM, and the LCM key performance parameters include particle size distribution, fiber aspect ratio, friction coefficient, compressive strength, soluble ability and high temperature resistance. Results of lab experiments and field test show that lost circulation control quality can be effectively improved with the optimal material selection based on the extracted key performance parameters of LCMs.

Research progress and application prospect of functional adhesive materials in the field of oil and gas drilling and production

By summarizing the composition,classification,and performance characterization of functional adhesive materials,the adhesion mechanisms of functional adhesive materials,such as adsorption/surface reaction,diffusion,mechanical interlocking,and electrostatic adsorption,are expounded.The research status of these materials in oil and gas drilling and production engineering field such as lost circulation prevention/control,wellbore stabilization,hydraulic fracturing,and profile control and water plugging,and their application challenges and prospects in oil and gas drilling and production are introduced comprehensively.According to the applications of functional adhesive materials in the field of oil and gas drilling and production at this stage,the key research directions of functional adhesive materials in the area of oil and gas drilling and production are proposed:(1)blending and modifying thermoplastic resins or designing curable thermoplastic resins to improve the bonding performance and pressure bearing capacity of adhesive lost circulation materials;(2)introducing low-cost adhesive groups and positive charge structures into polymers to reduce the cost of wellbore strengthening agents and improve their adhesion performance on the wellbore;(3)introducing thermally reversible covalent bond into thermosetting resin to prevent backflow of proppant and improve the compressive strength of adhesive proppant;(4)introducing thermally reversible covalent bonds into thermoplastic polymers to improve the temperature resistance,salt-resistance and water shutoff performance of adhesive water shutoff agents.

温敏形变纤维胶囊堵漏剂的开发及评价

针对现有玻璃纤维、聚丙烯纤维、剑麻纤维、陶瓷纤维等纤维材料的尺寸过大及加量过大导致水泥浆混拌过程中混配困难和浆体增稠的难题,研发了具有形状记忆功能的温敏形变纤维胶囊。当温度低于形变响应温度时,纤维胶囊的粒径较小,在漏失通道内形成高密度颗粒填充;当温度达到形变响应温度后,纤维胶囊激活发生膨胀变形,高密度颗粒之间相互挤压充填,在漏失通道内高强度架桥堆积,进而封堵漏失层。该纤维胶囊可将6 mm的纤维封装在3 mm的胶囊中,从而提高纤维材料在堵漏水泥中的有效含量及尺寸,改善水泥浆封堵能力,降低工作过程中的漏失风险,保证固井质量。加入温敏形变纤维胶囊堵漏剂的水泥浆流动度均值为22 cm,初始稠度为25 Bc,与纯水泥浆相似,相比于直接添加纤维材料,水泥浆体流态明显改善,可泵性大幅度增强,同时水泥石抗压强度也大幅提高,堵漏剂加量为5%时水泥石7 d的抗压强度可达50 MPa,解决了纤维水泥浆混配困难和浆体增稠的难题,对保证固井质量具有一定的实际意义。

水玻璃复合堵漏体系中氯化钙控释技术

水玻璃-氯化钙体系是常用的油井堵漏材料,但是水玻璃和氯化钙一接触即快速反应,只能采用双液法进行施工,工序复杂。因此拟对氯化钙进行控释,以期能够将水玻璃-氯化钙混合同时泵注,简化施工。该研究通过使用树脂体系对氯化钙进行包裹完成氯化钙的控释。通过改变体系中氯化钙的加量、交联剂的加量以及单体的种类及配比,考察以上3种因素对控释效果的影响。研究发现,通过树脂对氯化钙进行包裹时,氯化钙与单体的质量比为1∶4、交联剂加量为6%,可将水玻璃-氯化钙体系失去流动性时间延长至105 min。将已包裹氯化钙的树脂粉末进行二次包裹时,氯化钙与单体的质量比为1∶2、一次包裹二次包裹交联剂加量均为6%时,可将水玻璃-氯化钙体系失去流动性时间延长至110 min。在二次包裹的树脂体系中加入氯化钠,可将体系失去流动性时间延长至180 min。通过红外光谱和SEM谱图分析发现,吸水树脂通过减少氯化钙与水玻璃的接触面积来减缓反应的进行,树脂本身不参与水玻璃与氯化钙的反应进程。

高强度等四面体树脂固结堵漏剂的研制及应用

川渝地区在钻井过程中井漏频发,部分区域钻遇复杂地层发生恶性漏失,常常需要多次堵漏或多种堵漏工艺才能封堵成功,严重增加了钻井成本。通过对现有堵漏工艺进行分析,针对裂缝架桥填充原理,通过将高强度等四面体树脂作为主架桥材料、片状树脂及热固性树脂作为充填材料、纤维材料进行缠绕交联后研制成一种一袋式温控胶凝树脂固结堵漏材料YDFD。针对小裂缝,溶洞类、失返性(大裂缝)、呼吸性地层漏失情况,分别选用小、中、大3个型号的一袋式胶凝树脂固结堵漏剂进行级配,通过温控剂调节堵漏浆的固化时间保障施工安全、实现对漏层的精准封堵,在川渝油气井区处理井漏复杂过程中获得93%的一次堵漏成功率,达到了很好的应用效果,该工艺技术在油气田处理井漏难题时可推广应用。

自降解聚合物堵漏剂的合成与应用

钻井液漏失问题是长期存在于钻井作业中并且一直未能得到较好解决的技术难题,目前常用的聚合物凝胶堵漏材料存在承压能力低、吸水膨胀量小、抗温抗盐性差、不能自降解等缺点。为此优选了合成自降解聚合物堵漏剂的单体,通过正交实验确定了最佳合成条件,合成了自降解聚合物堵漏剂。该堵漏剂刚开始遇水膨胀率较小,能够快速进入裂缝部位产生封堵,随着时间的延长,体积不断膨胀,在裂缝处形成嵌压式封堵层,提高堵漏剂在裂缝性漏失层的滞留能力和封堵层的抗剪切强度。实验结果表明,该堵漏剂饱和吸水量最大可达156.9 g/g;21 d的降解率超过90%。在聚磺钻井液体系中分别加入5%的自降解堵漏剂和其它现有的几种堵漏剂后,针对3~5 mm的锲形裂缝,自降解堵漏剂钻井液体系承压压力可达17.5 MPa,堵漏效果明显优于现有堵漏剂;利用3 mm的裂缝性岩心模拟地层条件进行动态损害实验评价,岩心渗透率恢复值达到90%,且油气层保护效果良好。现场应用表明,该钻井液堵漏体系能够对裂缝型漏失地层实现良好的封堵,具有一定的应用前景。

旋转导向仪器用随钻堵漏剂

旋转导向仪器常被部分随钻堵漏剂堵塞筛网,造成井下仪器信号传递中断、井眼轨迹偏移、钻井液循环受阻等问题,且常用随钻堵漏材料易引起钻井液黏度大幅上涨,造成内耗大、滤饼厚等系列问题。因此要求随钻堵漏剂兼顾“可通过旋导”与“强封堵”性能且对钻井液黏度影响较小。以抗温植物纤维为原料,通过粉碎、筛析及疏水改性等步骤研发了一种随钻堵漏纤维(纤维1-1),依据行业标准评价其基本性能,并建立了一种随钻堵漏剂过旋导性能的评价方法。结果表明:纤维1-1基本性能均达到行业标准,其中,表观黏度增长率为10%,封闭滤失量为26 mL;加入纤维后钻井液循环30 min,压力增幅E<5%,具有良好的过旋导能力;在150℃、6 MPa实验条件下,加入3%纤维1-1的水基和油基钻井液体系能够封堵20~40目砂床,累计漏失量分别为4 mL和8 mL。最后,利用Zeta电位测试、微观形貌观察分析了纤维过旋导和堵漏机理。

钻井工程中井漏预防及堵漏技术

由于复杂的环境因素,在石油开采过程中,对钻井和修井的技术要求很高,一旦出现疏忽,很容易造成井漏事故。为解决我国钻井设备的井漏问题,满足能源输送需求,分析了井漏发生的原因,提出了相应的预防措施,并深入研究了井漏技术在钻井过程中的应用。

延迟膨胀颗粒堵漏剂的研究与应用

井漏是严重影响钻井生产正常进行的井下复杂情况之一，目前所采用的堵漏方法主要是桥塞堵漏和快干水泥堵漏，桥塞堵漏所采用的材料多由天然物质加工而成，它们的吸水膨胀能力较小或不具备吸水膨胀能力，在钻井堵漏时，往往易造成堵漏效果不佳和堵漏后发生重复性漏失。延迟膨胀颗粒堵漏剂WEA-1是一种吸水膨胀性很强的树脂，具有延迟膨胀的特征，因此能够保证颗粒材料有足够的时间进入井下漏失层位后继续膨胀，其吸水膨胀体积倍数可以达到4～8倍，同时，WEA-1的机械弹性形变能力强，拉伸强度大，封堵强度高，与各种水基钻井液配伍性好，能够达到良好的堵漏效果和有效提高地层承压能力的目的。延迟膨胀颗粒堵漏剂在彩南油田的C2872井、C3002井和霍001井进行了应用，堵漏均很成功，用WEA-1堵漏浆堵漏后，循环钻井液均再未发生漏失。

裂缝性地层堵漏配方及规律性研究

尽管国内外针对渗漏性漏失有过一些研究,但到目前为止,仍没有系统的针对裂缝性地层漏失的堵漏配方及规律性的研究,同时目前仍没有有效地解决裂缝性地层的漏失问题。在广泛调研国内外堵漏技术的基础上,利用自行研制的DL-A高温高压堵漏仪,对裂缝性漏层堵漏配方进行了研究,找到了裂缝性地层堵漏的一般规律,同时确定了较为理想的堵漏配方,为裂缝性漏层的堵漏技术奠定了基础。

堵漏型聚合物凝胶材料研究与评价

聚合物凝胶在油气井钻井过程中具有独特的排水堵漏作用。选择聚丙烯酰胺作为成胶剂,采用三价铬和酚醛作为交联剂,利用常规方法研究了聚合物凝胶的组成和性能,实验研究了聚丙烯酰胺分子量及浓度、交联剂类型和浓度对聚合物凝胶性能的影响,得出聚丙烯酰胺交联凝胶成胶最佳配比关系为:聚丙烯酰胺浓度为0.8%、铬交联剂加量为120 mg/L、交联温度为60℃。在此基础上对影响凝胶成胶性能的主要因素进行了探索实验,结果表明:水质对聚合物凝胶影响较小;pH值对凝胶的影响显著,在pH值为8时形成的凝胶粘度、稳定性较好,随着pH值升高,交联速度变快,成胶时间缩短;当盐浓度过高时,体系成胶性能变差,尤其是钙离子浓度高时,易形成果冻型块状沉淀。实验表明,聚合物凝胶时间的延长粘度损失小,具有稳定性好,流动性好等特点。通过高温高压失水仪砂床堵漏实验进一步证明,聚合物凝胶与其它堵漏材料配合,能够起到封堵漏层的良好作用。

固化承压堵漏剂在渤海油田断层破碎带的应用

渤海油田地层完整性差,断层破碎带井漏等裂隙性漏失是困扰钻井工程的一大技术难题。统计分析发现断层破碎带井漏占渤海油田全部井漏的16%,堵漏一次成功率仅为46.6%。针对断层破碎带井漏的特点,结合海上工程实际,研制出了一种堵塞形成快、滤饼强度高的酸溶性高失水固化堵漏剂STP。该堵漏剂选用酸溶性高失水材料复配架桥材料、特种纤维材料和固化剂组成,主要成分为亚硫酸盐和氧化物,不含聚合物,可直接用海水配制。室内评价和现场应用表明,该堵剂能够封堵断层破碎带等不同尺寸的裂隙性漏失,承压能力达7 MPa,对钻井液性能影响小,酸溶率80%以上,而且配制工艺简单,便于现场操作,非常适合海上油田断层破碎带堵漏。

诱导裂缝性井漏止裂封堵机理分析

承压堵漏过程中,堵漏材料进入缝内形成致密的封堵体,封隔井内压力与缝内压力之间的压力传播。利用达西定律和泊肃叶方程分别分析了缝内封堵体区域和缝内其他区域的压力分布;给出了堵漏材料承压封堵过程中诱导裂缝止裂的必要条件。通过缝宽与颗粒粒径比值和颗粒体积百分比雷诺数2个无量纲参数,可以建立堵漏材料封堵裂缝的封堵条件,堵漏材料的粒径和浓度需满足封堵条件曲线的下方区域才会形成稳定封堵体。承压堵漏效果不仅取决于堵漏材料的特性,还受到诱导裂缝性质的影响。因此,控制诱导裂缝性漏失中堵漏材料的优选需紧密结合诱导裂缝的特征。

钻井液堵漏材料及防漏堵漏技术研究进展

概述了近年来钻井液堵漏材料及防漏堵漏技术的研究进展。主要介绍了桥接、高滤失、柔弹性、聚合物凝胶、水泥浆、膨胀性典型钻井液堵漏材料及防漏堵漏技术的特点、作用机理和部分应用实例,并分析了钻井液堵漏材料及防漏堵漏技术研究的发展方向。

一种新型钻井防漏堵漏剂的研究与应用

以废橡胶制品为主要原料,经过特殊加工工艺和复杂的物理化学反应研制出了一种新型桥接型防漏堵漏剂,代号为LD,并进行了室内评价和现场试验。该防漏堵漏剂兼具颗粒和纤维形状,表面有凹凸,多毛刺,化学性质稳定,不易腐烂变质,具有一定的柔韧性和强度,密度低,惰性强,耐酸碱盐,抗高温,而且无毒无荧光。室内评价结果表明,该堵漏剂在正压差作用下能迅速形成有效封堵,封堵强度高、深度小,而且随钻加入钻井液中后对钻井液性能影响不大,并有利于降低钻井液高温高压滤失量,其岩心渗透率恢复率高。在长庆油田7个井次的现场试验表明,LD防漏堵漏剂具有良好的防漏、堵漏效果。与传统堵漏材料相比,LD防漏堵漏剂具有施工简便、封堵强度高、封堵有效期长、用量少,有利于降低钻井综合成本。