储层流体的热解定量描述方法

本文通过分析润油和润水储层岩石中不同性质原油相对渗透率和含水饱和度的关系，得出残余油、油水等产出点和束缚不水时各含油和度值，结合含油饱和度与总烃含量、有效孔隙度的理论关系式，建立了储怪流体的热解定量描述方法。该方法应用于生产实际见到了明显的效果。     

不同取心方法条件下的低渗透油层含油饱和度数据分析

含油饱和度是储量计算中的重要参数,通常通过岩心分析的方法来确定,油基泥浆取心分析的含油饱和度可信度高于水基泥浆分析的含油饱和度,但是油基泥浆取心成本太高。基于低渗透情况下储层自身密闭性良好的考虑,对比了油基泥浆取心和水基泥浆取心分析的原始含油饱和度,论证了在低渗透储层条件下,用水基泥浆取心替代油基泥浆取心确定储层原始含油饱和度的可行性。     

鄂尔多斯盆地姬塬地区长2油藏低含油饱和度成因

在储层含油饱和度测试资料的基础上,结合油源、油气成藏动力、储层物性及含油性分析,明确了鄂尔多斯盆地姬塬地区长2油藏低含油饱和度的成因机理。研究表明:研究区长2储层远离下部长7烃源岩生烃中心,油源不足是姬塬地区长2油藏含油饱和度低的根本原因;由于长2油藏构造幅度低,油气运移的动力较小,而且长2储层中束缚水饱和度较高,油气难以驱替,从而使得长2油藏含油饱和度低;此外,长2储层较强的非均质性,也是长2油藏低含油饱和度的原因。     

地化含油饱和度技术在雷64断块的应用

从储层地球化学原理出发,利用地化录井资料计算储层含油饱和度,进行储层解释与评价,尝试解释油、水层.该方法在雷64断块得到了成功应用.理论结果与实际试油结果吻合较好.利用该方法所得到的含油饱和度能客观、真实地反映储层含油饱满程度.地化含油饱和度技术对于油水层的正确解释与评价具有重要的指导意义.     

利用油基泥浆取心资料确定砂岩油藏原始含油饱和度若干问题探讨

原始含油饱和度是影响地质储量可靠性的重要因素之一。目前确定原始含油饱和度的方法主要有油基泥浆取心法、压汞法、测井解释和经验公式等四大类 ,其中油基泥浆取心是确定原始含油饱和度的第一手资料 ,也是用其它间接方法进行研究工作的基础和对比验证的依据。在用油基泥浆取心资料分析原始含油饱和度时 ,要充分考虑取心井所处油藏构造部位、储层特征及油水系统等多种因素的影响 ,并结合测井资料建立原始含油饱和度解释图版 ,对尽可能多的有效储层进行解释 ,最后采用有效孔隙体积权衡法选取油藏的平均原始含油饱和度值     

致密油充注过程中储层润湿性变化对含油性影响——以川中侏罗系致密油为例

以四川盆地川中侏罗系致密油储层岩心样品为例,开展了致密油微观充注物理模拟实验。实验模型采用砂岩薄片模型(尺寸为2.5 cm×2.5 cm,厚度约0.6 mm),将实验用油注入模型引槽中,压力由小到大逐步增加至每个模型出口端只出油不出水为止,观测渗流特征并计算含油饱和度。实验结果显示,充注前样品束缚水饱和度与充注后含油饱和度总和大于100%,基于核磁共振法对储层束缚水等流体饱和度与储层润湿性的分析,提出了充注前后储层润湿性的改变(水润湿转变为油润湿)使得最终含油饱和度高于被驱替的动水饱和度。致密油运聚过程中储层润湿性改变抵消了致密油储层高束缚水饱和度对致密油含油性的抑制作用,利于致密油运聚,是致密油成藏含油饱和度提高的重要原因。     

复杂断块油藏原始含油饱和度场分布模型研究

针对复杂断块油藏受储层非均质性、孔隙结构差异及流体毛管力等因素影响,导致原始含油饱和度分布空间差异难于准确表征的问题,基于岩样原始含油饱和度恢复资料,通过分析原始含油饱和度、束缚水饱和度对应毛管压力端点值与储层特征参数的相互关系,构建了原始含油饱和度、毛管压力端点值与储层流动区域指数、油柱高度的关系式,考虑油藏三维空间孔渗分布规律,建立了随储层特征参数变化的油藏原始含油饱和度场分布模型。研究结果表明,文中方法计算的开发早期井原始含油饱和度与测井解释结果绝对误差小于0.03。研究成果对精细表征复杂断块油藏原始含油饱和度场随储层空间变化的差异有重要意义。     

利用油基泥浆取心资料确定砂岩油藏原始含油饱和度若干问题探讨

原始含油饱和度是影响地质储量可靠性的重要因素之一。目前确定原始含油饱和度的方法主要有油基泥浆取心法、压汞法、测井解释和经验公式等四大类，其中油基泥浆取心是确定原始含油饱和度的第一手资料，也是用其它间接方法进行研究工作的基础和对比验证的依据。在用油基泥浆取心资料分析原始含油饱和度时，要充分考虑取心井所处油藏构造部位、储层特征及油水系统等多种因素的影响，并结合测井资料建立原始含油饱和度解释图版，对尽可能多的有效储层进行解释，最后采用有效孔隙体积权衡法选取油藏的平均原始含油饱和度值。     

核磁共振测井在古龙页岩油评价中的应用

古龙页岩油储层黏土含量高,孔隙结构较为复杂,微米-纳米孔喉及微裂缝发育,利用常规方法评价储层孔隙结构及物性、含油性具有较大难度。针对以上难题,在岩石物理实验基础上,提出了核磁共振变T₂谱截止值有效孔隙度计算方法和考虑小孔隙含油的二维核磁共振含油饱和度计算模型,并通过核磁共振区间孔隙度分析,厘清了古龙页岩储层孔隙结构。利用该方法计算的有效孔隙度平均相对误差为7.3%,含油饱和度平均绝对误差为4.0%,这不仅提高了计算储量关键参数的解释精度,还为后续开发提供了技术保障。该技术流程和方法对于类似页岩油的有效孔隙度和含油饱和度的评价同样具有指导意义,有助于推动页岩油等非常规油气资源的开发利用。     

致密油含油厚度定量计算方法

致密油不同于常规油藏上油下水、油水分界较明显,其含油饱和度一般随孔隙度增高而增大,同时离烃源岩越近含油饱和度也越高。因此,含油厚度不能简单地用油层顶到油水界面高度来表示,同时还要考虑裂缝对含油饱和度的影响。根据致密油的主要充注动力为生烃增压和毛细管压力差的特点,结合裂缝影响因素,应用渗流理论原理,建立了石油从烃源层直接渗入到致密储层深度的计算公式,应用加权平均方法计算致密油含油厚度。以中国石油3口井为例,计算各井致密储层的含油厚度,以此判断其含油情况,实践效果较好,为大面积致密油含油厚度评价提供了依据。     

注水开发油藏润湿性变化及其对渗流的影响

为提高水驱开发油藏采收率预测精度,研究了油藏岩石润湿性与相对渗透率之间的变化规律及其对两相渗流的影响。采用室内润湿性实验测定方法,对水驱开发油藏润湿指数与含水饱和度的关系进行了定量表征,导出了适合润湿性变化型油藏的两相渗流方程,建立了变润湿性水驱开发油田的采收率预测方法。润湿实验结果表明:所测岩心的润湿指数的对数与取心油层的含水饱和度呈近似线性关系。相对渗透率实验所测的代表低含水期到高含水期岩心的油水两相等渗点对应的含水饱和度由41%增加到53%,亲水程度增强。一维模型计算结果表明,含水率达到98%时,油润湿和强水润湿性油藏的预测采收率分别为52.7%和73.3%。研究揭示的水驱油藏岩石润湿性变化规律和建立的数学模型,可为更加准确地预测水驱油采收率提供参考。      

天然裂缝性油藏渗吸规律

为了研究渗吸作用对天然裂缝性油藏的影响,改善该类油藏的开发效果,以数值模拟为手段,通过建立概念地质模型,以静态和动态2种方式研究了毛细管压力、孔隙均匀程度、相渗曲线、基质和裂缝渗透率、原油黏度和基质含油饱和度对基质渗吸速度的影响,并在静态下对相关参数进行了公式拟合.静态下,渗吸速度与毛细管压力、基质渗透率、残余油饱和度、束缚水饱和度下的油相相对渗透率呈直线关系,与束缚水饱和度呈指数关系,与原油黏度呈幂指数关系;动态下,对于不同润湿性的油藏提出了不同的开发方式.     

The effect of wettability heterogeneity on capillary pressure and relative permeability

The effect of wettability on fluid flow properties in porous media has been extensively studied, and is still a subject of highly active investigation. Most of the work has focused on cores of homogeneous wettability. Little attention has been paid to wettability heterogeneity effects at the core or pore scale. In a previous paper, we reported on a series of centrifuge experiments performed to study the effect of wettability heterogeneity on capillary pressure. An experimental technique, named cyclic aging, was developed to create regions of different wetting in the same core sample. In this paper, the work is extended to study the effect of wettability heterogeneity on both capillary pressure and relative permeability curves using centrifuge, continuous injection and steady state techniques.The experimental procedure consists of three steps: (1) the core plug is fully saturated with brine and subsequently a drainage experiment is performed targeting an initial oil saturation S_oi, (2) after aging, oil is displaced by water to residual oil saturation S_or, and (3) oil is injected targeting higher initial oil saturation. In the secondary drainage experiment (step 3), oil first displaces water from the pores exposed to crude oil in primary drainage (step 1) and then enters fresh pores not exposed to crude oil before.In our previous study, it was found that wettability heterogeneity caused a step change in capillary pressure which correlated very well with the saturation at which wettability contrast was expected. However, the height of the step could not be explained by wettability contrast and/or water trapping alone. An experimental artifact caused by the centrifuge technique made the step higher than expected. The experimental artifact was the result of the nonuniform saturation profile developed across the core at the end of the centrifuge experiment. In this study, new techniques were used which resulted in a uniform saturation profile along the core sample during the primary drainage experiment. It was found that in this case the step in the capillary pressure is determined by wettability contrast and water trapping. It was also found that the relative permeability curve changes its characteristics when oil accesses the pores not previously exposed to crude oil.The results of this study show that (1) only the part of the pore space exposed to crude oil undergoes wettability changes on both core scale and pore scale, and (2) ignoring wettability heterogeneity can lead to large errors in the estimated two phase flow functions with important consequences with respect to fluid flow in porous media.     

考虑岩石润湿性的新导电模型研究

考虑岩石的润湿性,用连续函数模拟油珠表面和孔隙表面的接触关系,提出了新的岩石导电模型(CWRM)。当油珠进入具有不同孔喉尺寸岩石模型后,由于岩石具有的润湿性,油珠和岩石孔隙表面可能具有不同的接触方式。在水润湿性的储层中,油珠和孔隙表面之间会有水膜,水膜保持了连续的导电路径,因此,水润湿性岩石中常会形成低电阻率。相反,在油润湿性岩石中,油珠与岩石孔隙表面紧密接触,可能完全堵死孔喉,导致岩石电阻率异常地增高。所以,即使在含油饱和度相同的情况下,岩石的电阻率也会因为润湿性不同而显著地变化。根据阿尔奇公式和CWRM模型,在考虑岩石润湿性的情况下,计算了岩石模型的含水饱和度。计算结果表明,使用阿尔奇公式和CWRM计算的含水饱和度,其差值可达10％或更高。对于水润湿和油润湿岩石,根据CWRM计算的I一Ww关系在双对数坐标中都是曲线关系。CWRM模型和结论均被野外数据和实验室数据所证实。     

低渗透油藏渗流物理特征的几点新认识

对于低渗透油藏,油水界面张力、岩石润湿性和孔喉比是影响产量和采收率的重要因素,而润湿指数和润湿角通过毛管数与驱油效率有直接的定量关系。该文提出了一个关联着界面张力、润湿性和孔喉比的修正毛管数概念,建立了基于Amott润湿指数与USBM指数的润湿角表征方法,继而推导出低渗透储层毛管数表达式,并通过岩心实验确定出其与残余油饱和度的关系。以此为基础给出不同界面张力与润湿情况下的相对渗透率曲线、驱油效率和注入能力的计算公式,揭示了各种油藏物理参数之间的关联性,为优化低渗透油层化学驱改变界面张力、润湿性控制参数,进而为提高驱油效率和采收率提供了理论依据。     

Dimensionless groups for three-phase gravity drainage flow in porous media

The downward displacement of oil by gas (either through gas cap expansion or by gas injection) at the crest of the reservoir is an attractive method of oil recovery. The drainage of oil under gravity forces is a potentially efficient method as it can reduce the remaining oil saturation to below that obtained after waterflooding. This paper describes a series of experiments of gas invasion under gravity-dominated conditions with special attention to the effects of wettability and water saturation on three-phase flow. The experiments were performed in bead-pack models by spontaneous gas invasion at both low and high water saturations with a spreading oil. Different oil recovery rates were observed depending on the wettability of the beads and initial water saturation. At irreducible water saturation, the process appeared to be less efficient for the oil-wet conditions, while similar oil recoveries are observed for both oil-wet and water-wet media at residual oil saturation. Different recovery rates occur with different fluid morphology, which depend on the matrix wettability and the balance between gravity, viscous and capillary forces. The results have been analysed using dimensionless groups. The Bond (N_B) and capillary numbers (N_C) were modified to include the 3-phase effects of gas, oil and water. However, for these cases the Bond and capillary numbers alone were insufficient to fully describe the dynamics of oil recovery by gravity drainage. Therefore, a new dimensionless group combining the effects of gravity and viscous forces to capillary forces was defined as: N=N_B+A(μ_d/μ_g)N_C, where A is a scaling factor (in all our experiments A=−17225) and (μ_d/μ_g) is the viscosity ratio between the displaced and displacing phase. A linear relationship was found between this new group and the total recovery for all the scenarios tested. The slope was approximately 40 for three cases, i.e., water-wet case at irreducible water saturation, and water-wet and oil-wet cases at residual oil saturation. The oil-wet case at irreducible water saturation has a larger slope, probably due to the blocking effect of water. These experimental results may be used as a benchmark to test theoretical models of three-phase flow under gravity dominated conditions. The new dimensionless group should improve the understanding of the pore scale mechanisms so that these processes can be included in the development of network models and in the processes of upscaling laboratory results.     

蒸汽驱对储层润湿性的影响

储层润湿性决定着注入流体在储层中渗流的难易程度,对原油的驱油效率、采出程度起着决定性作用。为了明确蒸汽驱过程中储层润湿性的变化,通过室内实验非稳态法水驱油、蒸汽驱油测定油藏相对渗透率曲线的变化,研究了疏松砂岩油藏蒸汽驱对储层润湿性改变的影响。实验结果表明,由水驱到蒸汽驱,油相相对渗透率增加,残余油饱和度下降,残余油饱和度对应的水相相对渗透率增加,等渗点右移;综合相对渗透率曲线特征表明,蒸汽驱使得储层润湿性向亲水方向发展。通过非稳态法研究相对渗透率曲线,由相对渗透率曲线特征点的变化来判断储层润湿性的改变简单易行,蒸汽驱对储层润湿性的改善非常有利。     

影响冻胶类堵剂封堵性能的因素分析

该文概要介绍了国内外有关影响冻胶类堵剂封堵性能的因素的研究情况，具体分析了冻胶类型及组成、岩心含油饱和度、渗透率、岩石的润湿性、驱替相类型对堵剂封堵性能和堵水调剖效果的影响，表明冻胶本身的结构特性是影响冻胶封堵率的根本因素；冻胶的封堵率随着岩心含油饱和度的增加而减小，同时受到岩石的润湿性和驱替相类型的影响；冻胶对亲水岩石的封堵率大于对亲油岩石的封堵率，对水相的堵塞程度大于对油相的堵塞程度。在此基础上推导出了调剖堵水施工中堵剂封堵率的计算公式。     

Effect of wettability on oil recovery and breakthrough time for immiscible gas flooding

The effect of wettability on oil recovery at higher water saturation is still not fully understood, especially in the case of mixed wettability. This study was conducted to examine the effects of wettability on oil recovery and breakthrough time through experiments for two wettability conditions (water-wet and mixed-wet) and three water saturations (20%, 40%, and 60%). Clashach sandstone core with a porosity of 12.8% and a permeability of 75 md was utilized as the porous media. Immiscible gas flooding was performed by injecting nitrogen gas into the core at room temperature and pressure. The results showed 54.3% and 48.8% of the initial oil in place (IOIP) as the ultimate oil recovery at 40% water saturation from mixed-wet core and water-wet core respectively. In contrast, the water-wet core displayed better results (32.6% of the IOIP) in terms of breakthrough time compared to the results of water-wet core (10.6% of the IOIP) at the same water saturation. In conclusion, oil recovery was found highly dependent on water saturation while breakthrough time was mainly affected by the wettability of the cores.     

碳酸盐岩气层岩电参数实验

储层含油气饱和度是储量评价的基础。在以Archie公式为核心的储层含油气饱和度评价方法中,岩电参数是Archie公式应用的基础。通过开展岩电参数研究实验,对利用风干法和自吸增水法建立碳酸盐岩岩心含水饱和度进行了对比。研究结果表明,由于碳酸盐岩岩心孔隙结构、润湿性复杂,依靠自吸水方式,含水饱和度高于一定值后岩心将表现出不再自吸水的现象。自吸增水法所能够达到的最高含水饱和度一般都低于50%,相对于自吸增水建立的岩心低含水饱和度时的电阻率,被模拟地层水100%饱和时的岩心电阻率R_o 普遍偏高,100%饱和状态下的岩心电阻率大都偏离了低饱和度数据点拟合线的延长线。风干法和自吸增水法获得的指数n和系数b数值上具有明显区别,但变化趋势一致,且两种饱和度建立方法获得的指数n都与孔隙度具有较高的相关性,且都随孔隙度增大而降低。对基质孔隙度、渗透率都差的碳酸盐岩储层岩石的岩电研究中,含水饱和度建立十分困难。根据碳酸盐岩气藏成藏后气水运移规律及气藏内部气水平衡过程,风干法所获得的岩电实验关系更符合碳酸盐岩气藏含气饱和度评价的需要。