钻井液处理剂及体系对泥页岩坍塌压力的影响研究

水基钻井液通常使泥页岩坍塌压力增加,研究钻井液及处理剂体系对地层坍塌压力的影响有助于研究优选防塌钻井液处理剂及体系.介绍了通过岩心力学性能测试分析计算地层坍塌压力的方法,研究了部分处理剂对地层坍塌压力的影响,认为增强抑制和封堵能力可降低地层坍塌压力.文中提出的钻井液处理剂及体系对泥页岩坍塌压力影响的研究方法是切实可行的,可用来优选研究防塌钻井液处理剂、优选防塌钻井液体系、确定合理的防塌钻井液密度.研究表明,在聚合物或聚磺钻井液中加入抑制剂(如KCl)和粒度及软化点适当的封堵材料可降低地层的坍塌压力.     

欠平衡钻井坍塌压力计算模型

欠平衡钻井过程中井壁稳定是保证欠平衡钻井成功的关键。在欠平衡钻井过程中，地层流体不断流入井内，促使井筒周围的应力将伴随地层流体的流入而重新分布，进而影响井壁的稳定性。根据原地应力产生的应力与地层流体向井眼径向流动产生的拖拽力叠加而求得了欠平衡钻井井周应力的解析解，考虑欠平衡钻井过程中地层流体对岩石拖拽作用后地层坍塌压力更大即井壁更易失稳，运用Mohr-Coulomb强度准则建立了欠平衡钻井坍塌压力的计算模型。将所建立的计算模型应用于塔中722井的井壁稳定性分析，结果表明：理论分析结果与工程实测数据对比，计算结果较为准确。     

砂岩气藏水基欠平衡钻井逆流自吸效应实验研究

采用水基钻井液欠平衡钻开砂岩气层时，欠平衡压差往往并不能完全抵消岩石的自吸毛细管力，从而产生逆流自吸效应。这种自吸效应可能对砂岩气藏水基欠平衡钻井的储层保护效果产生影响，但目前与之有关的实验研究还很缺乏。为此，设计了一套实验装置，模拟水基欠平衡条件，研究了砂岩基块孔隙逆流自吸规律及其影响因素。结果表明，水基欠平衡钻井过程的逆流自吸效应引起岩石气相渗透率降低，削弱欠平衡钻井的储层保护效果；欠平衡压差越小，逆流自吸作用越强，过小的欠压值不能起到欠平衡钻井保护储层的作用；随着逆流自吸时间延长、围压增加和黏土矿物膨胀，逆流自吸导致气相渗透率下降的程度加剧；逆流自吸引起的气相渗透率下降速率可以表示成时间的幂函数。     

液体欠平衡钻井中的储层损害研究

目前中国针对欠平衡钻井的油气藏损害类型和方式进行的研究工作还比较少,这必然会阻碍欠平衡钻井技术的进一步发展。通过液体欠平衡钻井中逆流自吸和短时间过平衡对储层的损害实验,分析了液体欠平衡钻井中储层损害的主要方式及损害程度。结果表明,保持连续欠平衡状态,逆流自吸作用对储层的损害较小,短时间过平衡可以对裂缝储层造成较为严重的损害。     

水基硅酸盐钻井液的页岩井眼稳定性研究

结合室内实验数据,分析了硅酸盐钻井液粘土稳定作用的主要影响因素。结果表明,硅酸盐的模数在2.8—3.2、加量在3％—5％时钻井液抑制性能较好,无机盐与硅酸盐的协同效应提高了硅酸盐的抑制性能。提出硅酸盐稳定页岩井壁的机理为:硅酸盐形成凝肢与沉淀堵塞微裂缝与页岩孔隙,阻止滤液进入地层,减少压力穿透;抑制粘土矿物水化膨胀与分散;与无机盐协同作用阻止水进入地层;与粘土矿物反应导致渗透率降低等。     

水化应力和滤饼质量对地层坍塌压力的影响分析

在井眼力学化学耦合稳定性评价的基础上，考虑了滤饼质量因素后，对坍塌压力变化进行了对比分析，结果表明，地层坍塌压力当量密度有一定的变化。给出了考虑水化作用和滤饼质量后预测井壁稳定性的方法，同时将该方法应用于现场，取得了较好的预测效果。     

页岩水化对其力学性质和井壁稳定性的影响

在对新疆油田呼图壁地区防塌钻井液配方进行优选的基础上,进一步研究了钻井液引起的水化与泥页岩力学性质和井壁稳定性的关系。试验和计算结果表明,泥页岩水化后由于抗压强度降低,粘聚力下降,因而对钻井液安全密度窗口有显著的影响。以呼002井泥页岩为例,水化后坍塌压力所对应的钻井液密度值提高了0.23g/cm3,破裂压力所对应的钻井液密度值降低了0.15g/cm3。在相同的试验条件下,泥页岩水化程度与钻井液类型有关。在所使用的3种防塌钻井液中,KCI两性离子聚磺钻井液对泥页岩的抑制作用为最好.     

硬脆性泥页岩非壁稳定剂的研究

针对辽河油田双等地区井壁示稳定问题，研制了一种硬脆性泥页碉井壁稳定剂－ＪＨＳ。这是一种含阴，阳，非离子和有机硅等基团的多元共聚物。室内研究结果表明，ＪＨＳ对辽河油田沙河街组硬脆性泥页岩具有很好的稳定性，其２４ｈ径向膨胀度较稳定剂Ｋ－ＰＡＭ等可降低１０％左右，热滚回收率较Ｋ－ＰＡＭ等约提高１０％以上。     

聚醚多元醇对泥页岩地层坍塌压力影响实验研究

应用三轴岩石强度测试仪RTR-1000实验研究现有钻井液及改进钻井液体系对阜宁组泥页岩力学性质和强度特性的影响,并计算比较其对坍塌压力的影响,优选出能够降低地层坍塌压力的钻井液体系。实验所用岩心为苏北阜宁组露头岩心,实验结果表明：在钻井液中加入聚合醇或聚醚多元醇产品,利用其浊点效应对地层进行封堵,改进后的钻井液体系能够提高地层岩石的强度,降低地层坍塌压力（当量钻井液密度）0．19-0．30g／cm^3,扩大了安全钻井液密度范围。     

A New Approach for Specifying Imbibition Face Boundary Condition in Countercurrent Spontaneous Imbibition

Abstract

Countercurrent spontaneous imbibition is one of the basic processes in two-phase fluid flow in fractured porous media. Many researchers have studied modeling of this phenomenon and analytical and numerical solutions have been presented. Specifying the imbibition face (open face) wetting phase saturation, which acts as a boundary condition, has been one of the main challenges in this area. There is no method to specify the imbibition face boundary condition satisfactorily. In this study a new logical method is introduced to determine the open face boundary condition that is satisfactorily close to experimental results. This method considers different aspects of the process of countercurrent spontaneous imbibition and, based on formulation and effective forces in this process, three pieces of evidence are presented to prove that the wetting phase saturation at the imbibition face is a value that leads to maximum wetting phase and nonwetting phase flow with respect to saturation. Because flow rates in this process are a function of saturation and gradient of saturation with respect to location, the maximum wetting and nonwetting phase flow with respect to only saturation would not lead to maximum reachable flow rates for the process.     

The Influence of Surfactant Solution Injection in Oil Recovery by Spontaneous Imbibition

Imbibition is the spontaneous displacement of fluids through porous media that occurs until capillary equilibrium is reached. Factors such as wettability and high interfacial tensions may negatively affect the process, requiring additional work to enhance oil recovery. This work aims to explain some aspects of the dynamics of oil recovery by spontaneous imbibition using different fluids. Static imbibition and contact angle experiments were performed using sandstones of the Botucatu Formation (Brazil). The plug samples were exposed to immersion in brine and in surfactant solutions, and the progression of oil recovery was monitored with time. The results showed that the capillary imbibition rate and the oil recovery factor were higher when an ionic surfactant was used. The inverse Bond number and the shape of the recovery profile showed different trends of the capillary imbibition dynamics. Higher oil recovery factors for ionic surfactant were also an effect of the contact angles observed.     

气体钻井条件下泥页岩自发吸水规律研究

单相渗流、总吸附水量相关法不能够模拟气水两相渗流,为此,建立了气水两相渗流模型,分析了气体钻井过程中当地层存在气饱和砂岩、气饱和泥页岩夹层时泥页岩的自发吸水规律.采用有限差分法对所建模型进行了求解,并绘制了含水饱和度、孔隙水压力和孔隙气压力的时空分布曲线.对比垂直向上、向下自发吸水规律可知,重力作用可以忽略不计,将计算的吸水质量与试验结果进行对比,结果较为吻合,从而验证了所建模型的正确性.     

Numerical Model of Countercurrent Spontaneous Imbibition in Underbalanced Drilling: Formation Damage Investigation

Abstract

Although mud filtrate invasion is mostly concerned in overbalanced drilling (OBD), it is shown that it also occurs during underbalanced drilling (UBD) operations. UBD is a drilling operation in which the hydrostatic head of a mud column is maintained at a pressure less than that of fluid in the porous medium. Formation damage due to mud invasion in OBD could be eliminated in UBD. However, this benefit of UBD can be missed when pressure suddenly turns to overbalance and/or spontaneous imbibition. During UBD it is difficult to maintain mud pressure less than formation pressure especially for short periods of time for operational reasons such as bit trips, and it will cause major damage due to nonexistence of internal and external mud cake. Also, spontaneous imbibition, which occurs in low-permeable reservoirs, causes drilling fluid invasion. In this case, the hydrostatic head of drilling mud is less than formation pore (oil phase) pressure, but it may be higher than water-phase pressure in the formation because of capillary pressure. This causes the flow of water into the formation, which causes formation damage. The aim of this study is to present a model for spontaneous imbibition of water into the water-wet formation during underbalanced drilling and to investigate the effect of drilling fluid, reservoir rock, reservoir fluid, and drilling operation parameters on the extension of damage in nonfractured formations. The numerical solution of governing equations and sensitivity analysis on different parameters are presented. The results show that in the case of strong capillary pressure, (1) the damage due to spontaneous imbibition is considerable and (2) the most effective criteria are temporary overbalanced and static drilling fluid situations where both increase the extend and amount of drilling filtrate invasion. Also, it was concluded that a low UBD pressure difference causes damage, whereas the very high UBD pressure difference is inefficient.     

低渗透油藏渗吸采油技术研究进展*

针对低渗透油藏渗吸采油技术,运用文献调研的方式,介绍了渗吸采油相关概念,综述了低渗透油藏渗吸 采油技术在渗吸机理和应用方面的研究成果与最新研究进展,对低渗透油藏渗吸采油技术在室内实验和现场应 用中的发展趋势进行了技术展望。     

三塘湖盆地芦草沟组页岩自吸特征

页岩储集层压裂后,存在压裂液返排率低、产能差异大的特点,大量的压裂液长期滞留井下并被储集层自发吸入,对油气开发及有效动用具有很大影响。以页岩油可动性、页岩静态自吸和润湿性等多项实验为基础,通过页岩自吸压裂液驱油实验和恒压水驱油实验,认识到页岩独具的自吸特征。基于静态自吸实验,从页岩基本吸水物理现象入手,通过自吸饱和度和自吸速率2个自吸特征参数来反映页岩的自吸能力,分析现场压裂后生产排液曲线,认为室内实验结果对页岩压裂后生产排液有一定的预测作用。通过液—岩铺展性实验,分析了三塘湖盆地二叠系芦草沟组页岩润湿性特征及其对自吸能力和特征的影响,认识到页岩既有亲油性又具有亲水性的混合润湿特征,结合相关资料综合分析认为,页岩的自吸能力和特征主要受微观孔隙结构和润湿性的共同控制和影响。     

页岩油水平井压裂渗吸驱油数值模拟研究

为了提高压裂页岩油水平井产量预测精度、优化闷井时间及压裂液用量等参数,建立了一种考虑压裂液注入、闷井渗吸及开井生产的压裂页岩油水平井油水两相渗流数学模型,利用控制体积有限元法求其数值解,模拟了渗吸作用下基质–裂缝油水置换的过程,获得了油水压力场、速度场、产量及含水率的动态变化.分析了压裂渗吸驱油特征,优化了闷井时间和压...     

基于核磁共振技术研究表面活性剂提高吉木萨尔页 岩油渗吸效率*

为评估表面活性剂提高吉木萨尔凹陷芦草沟组页岩油渗吸效率潜力,研究其微观动用特征,本文采用低场 核磁共振成像系统研究了阴离子表面活性剂Surf-L在不同润湿性天然页岩油岩心渗吸效率和不同孔隙中含油 饱和度随时间的变化。核磁共振T₂谱结果表明,质量分数为0.1%的阴离子表面活性剂Surf-L能有效提高吉木萨 尔页岩油藏岩心的渗吸效率。对于中性润湿性的匀质粉砂岩岩心S52,胍胶溶液和含Surf-L的胍胶溶液主要动 用大、中孔隙内原油。其中,渗吸效率贡献率最大的是大孔隙,其次是中孔隙。含Surf-L的胍胶溶液可以有效动 用中、小孔隙内原油,最终渗吸效率比胍胶溶液提高6.95百分点。对于亲油的砂质云岩岩心S39,胍胶溶液主要 动用大孔隙内原油,而含Surf-L的胍胶溶液能有效动用中、小孔隙内原油,最终渗吸效率比胍胶溶液提高18.89 百分点。表面活性剂渗吸过程可分为前期、中期和后期3个阶段：渗吸初期,中孔隙的贡献率最大为61.7%;渗吸 中后期,大孔隙的贡献率逐渐上升。同时,胍胶溶液渗吸平衡时间约为51 h,而含表面活性剂的胍胶溶液渗吸平 衡时间约为100 h。无论是中性润湿岩心还是亲油性岩心,相对于胍胶溶液,含表面活性剂的胍胶溶液通过有效 动用中、小孔隙内原油,可进一步提高页岩油藏渗吸效率。     

表面活性剂对低渗油湿灰岩表面性质及渗吸行为的影响

裂缝发育的低渗灰岩储层，当基质岩块为混湿及油湿时，毛细渗吸驱油作用很弱。本工作采用毛管上升、渗吸及相对渗透率曲线方法，在62℃下研究了CTAB和SDBS溶液对油湿灰岩表面性质及渗吸行为的影响。浓度为700mg／L时，SDBS溶液与原油间的界面张力为0．035mN／m，而CTAB溶液为1．25mN／m；随着浓度增大，SDBS溶液使亲油的毛管表面润湿接触角缓慢减小，而CTAB溶液使润湿接触角大幅减小，在与最大吸附量对应的浓度下润湿接触角有最低值；亲油岩心在CTAB溶液中的渗吸驱油速度较SDBS溶液中的渗吸驱油速度高；相渗曲线表明，与亲油岩心／SDBS溶液体系相比，亲油岩心／CTAB溶液体系的油相相对渗透率较高而水相相对渗透率较低。因此，CTAB类阳离子表面活性剂可望用于该类油藏的开发。讨论了相关的机理。图6参10。     

页岩油储层层理缝渗吸机制和渗吸模式

页岩油主要采用水平井分段压裂形成纵向缝(构造缝)的开发理念,并未考虑开启层理缝的渗吸作用。为进一步研究层理缝对页岩油开发的作用,以新疆吉木萨尔地区页岩油为例,通过岩心渗吸模拟实验、铸体薄片观察、CT扫描等方法,分析层理缝、构造缝渗吸效率。结果表明:构造缝模型渗吸深度为1.5 cm,层理缝模型渗吸深度可达1.0 cm,层理缝在表层渗吸效率较高;在开启构造缝的基础上开启同样面积的层理缝,渗吸效率可提高4.3%左右;根据渗吸物理模拟实验,建立起构造缝与层理缝不同的油水渗吸转换模式,表明在构造缝渗吸的基础上,利用层理缝的渗吸作用,可大大提高页岩油的开发效率。该研究为页岩油藏优化压裂方式、提高页岩油采收率提供了理论依据。