Numerical simulation of the dual laterolog for carbonate cave reservoirs and response characteristics

Cave carbonate formations are characterized by heterogeneity, which makes electrical log prediction difficult. It is currently important to know how to use the dual laterolog to accurately identify and quantitatively evaluate caves. Using numerical simulation to calculate electrical log responses can provide a theoretical basis for cave identification and evaluation. In this paper, based on the dual laterolog principles, we first study different size spherical cave models using the finite element method （FEM）, determine a relation between resistivity and cave filling after comprehensively studying the log responses of cave models with different filling material, and finally study the dual laterolog responses on caves filled with shale, limestone, conglomerate, and thin laminated formation of sand and shale. The numerical results provide a theoretical basis for identification and evaluation of carbonate cave reservoirs.

Assessment and optimization of fracture-karst cave connectivity in horizontal well hydraulic fracturing of carbonate reservoirs

The karst cave serves as the primary storage space in carbonate reservoirs.Simultaneously connecting multiple karst caves through hydraulic fracturing is key to the efficient development of carbonate reservoirs.However,there is lack of systematic research on the mechanisms and influencing factors of fracture propagation in car-bonate rocks.This paper established models including karst cave models,single natural fracture-cave models,and multiple natural fracture-cave models based on the discrete lattice method.It thoroughly studied how geological and operational factors affect the fracture propagation and the connectivity of karst caves.The final step involved establishing a prototype well model and optimizing operation parameters.The research indicates that an increase in the Young's modulus and pore pressure of karst cave could facilitate hydraulic fracture connecting with caves.When the pore pressure is lower than that in the matrix,it will generate a repulsive effect on hydraulic fractures.The natural fracture along the hydraulic fracture path significantly facilitates the connection with caves.When the wellbore azimuth is less than 60℃,the fracture's diversion radius is small,and hydraulic fractures primarily connect with karst cave through natural fractures.When the wellbore azimuth exceeds 60℃,the fracture's diversion radius increases.Under the combined action of hydraulic fractures and natural fractures,the stimulated volume of the karst cave noticeably increases.Under the same liquid volume,increasing the injection rate could enhance the cave stimulated volume.Combining the findings from numerical simulation studies resulted in the development of a diagram that depicts the connectivity of karst caves,providing valuable insight for hydraulic fracturing operations in carbonate reservoirs.

Characteristics and development model of karst reservoirs in the fourth member of Sinian Dengying Formation in central Sichuan Basin,SW China

The reservoir space,types and distribution characteristics of karst carbonate gas reservoirs in the fourth member of Sinian Dengying Formation(Deng 4 Member)in central Sichuan Basin are analyzed based on the drilling,logging and seismic data.A development model of karst reservoirs is constructed to support the high-efficiency development of gas pools.The research shows that the reservoirs in Deng 4 Member have mainly small-scale karst vugs and fractures as storage space,and can be divided into three types,fracture-vug,pore-vug and pore types.The development patterns of the karst reservoirs are determined.On the plane,the karst layers increase from 65 m to 170 m in thickness from the karst platform to the karst slope,and the high-quality reservoirs increase from 25.0 m to 42.2 m in thickness;vertically,the reservoirs at the top of Deng 4 Member appear in multiple layers,and show along-bedding and along fracture dissolution characteristics.The reservoirs at the bottom are characterized by the dissolution parallel to the water level during the karstification period,and have 3-5 large-scale fracture-cave systems.Based on the reservoir development characteristics and the genetic mechanism,three types of reservoir development models of karst reservoir are established,i.e.,bed-dissolved body,fracture-dissolved body and paleohorizon-dissolved body.The construction of karst reservoir development models and seismic response characteristics of the three types of reservoirs can provide parameter for well placement and trajectory design,and substantially improve productivity and development indices of individual wells and gas reservoirs.The designed production capacity of the gas reservoir has enhanced from the initial 3.6 billion to 6 billion cubic meters,making the profit of the reservoir development increase noticeably.

Experiments on the influences of well pattern on water flooding characteristics of dissolution vug-cave reservoir

Based on the similarity criterion, volcanic rock samples were taken from outcrops to make experimental models. Water flooding experiments of five-spot well pattern, nine-spot well pattern, five-spot to nine-spot well pattern, the relationship between relative well and fracture positions, and injection rate in dissolution vug-cave reservoirs with/without fractures were carried out to analyze variation regularities of development indexes, find out development characteristics of water flooding with different well patterns and sort out the optimal water flooding development mode. For dissolution vug-cave reservoirs without fractures, five-spot well pattern waterflooding has very small sweeping area, serious water channeling and low oil recovery. When the well pattern was adjusted from five-spot to nine-spot well pattern, oil recovery could be largely improved, but the corner well far from the injector is little affected. In dissolution vug-cave reservoirs with fractures, when the injector and producer are not connected by fractures, the fractures could effectively connect the poorly linked vugs to improve the development effect of water flooding. Whether there are fractures or not in dissolution vug-cave reservoirs, the development effect of nine-spot well-pattern is much better than that of five-spot well pattern and five-spot to nine-spot well pattern, this is more evident when there are fractures, and the edge well has better development indexes than corner well. At the high-water cut stage of water flooding with nine-spot well pattern, the oil recovery can be further improved with staggered line-drive pattern by converting the corner well into injection well. It is helpful to increase the oil production of corner well of nine-spot well pattern by increasing the injection rate, and improve ultimate oil recovery, but the water-free production period would be greatly shortened and water-free recovery would decrease.

塔河油田良里塔格组迷宫型岩溶洞穴系统发育特征

为了明确塔河油田上奥陶统良里塔格组迷宫型岩溶洞穴系统的样式和结构,利用古地貌恢复、古水系刻画、测井地层对比、构造断裂解析、地震属性刻画等方法,进行了塔河油田11区的古水文地貌恢复、岩溶层组格架构建、岩溶洞穴识别和成因模式分析。结果表明:塔河油田南部加里东运动中期Ⅱ幕古地貌西北高、东南低,发育北北西—南南东向树枝状地表深切沟谷,良里塔格组发育近水平状分布、闭合管道结构及溶蚀强度较高的迷宫型岩溶洞穴系统;良里塔格组岩溶洞穴系统与澳大利亚Judbarra地区Bullita洞穴系统成因相似,属于典型的表生岩溶扩散下渗型迷宫型岩溶洞穴系统;上奥陶统恰尔巴克组泥岩段为隔水层,控制了良里塔格组迷宫型岩溶洞穴系统的侧向溶蚀作用;沟通地表水系的断裂为岩溶水主要下渗溶蚀通道,随着区域基准面下降,岩溶水沿断裂下渗进入中奥陶统,中奥陶统一间房组形成断溶体。塔河油田加里东运动中期Ⅱ幕表生岩溶“双层”迷宫型岩溶洞穴系统的认识对上奥陶统油藏开发具有重要意义。

塔里木盆地顺北1号断裂带奥陶系碳酸盐岩储层结构表征及三维地质建模

综合利用地震、测井、岩心以及动态生产资料,对塔里木盆地顺北1号断裂带断控型碳酸盐岩储集体的内部结构进行了层级划分;基于层级划分,通过地震资料属性提取与转换、深度学习、基于目标示性点过程模拟以及离散裂缝网络模拟(DFN)等方法建立了三维地质模型,并以模型进行油气储量和油藏数值模拟,将拟合结果与实际生产数据进行对比。研究结果表明:(1)顺北1号断裂带奥陶系断控型储层按层级由大到小分为走滑断裂影响带、断控体、类洞穴、类洞穴内簇充填和裂缝带共5个层级。(2)走滑断裂影响带受应力差异影响具有分段性,可细分为挤压段、拉分段和平移段;断控体在拉分段发育断裂交会型、单支走滑型,在平移段发育双断裂交错型和两断裂交会型,在挤压段发育双断裂扭曲型和双断裂交会型,共有6种平面组合样式;类洞穴在地震剖面上呈串珠状反射特征;类洞穴内部分为栅体与栅间(基岩),其中栅体又可进一步分为簇(角砾带)、簇间(裂缝带),整体表现为栅状结构,簇的物性更好;裂缝带为类洞穴的主要储集空间,在簇内部比簇间更发育,在一间房组比鹰山组更发育,一间房组和鹰山组均以发育高角度裂缝为主,在两者连接处则以发育水平缝为主。(3)地质模型预测的油气储量与地质分析储量误差为1.75%,模型模拟的生产井地层压力及累产液结果与生产动态吻合度较高,拟合误差小于10%。

超深断控储集体储层连通性的地震描述方法

新疆塔里木盆地顺北地区发育埋藏深度超7000 m的碳酸盐岩断控缝洞储集体,储集体内部非均质性强,地震资料成像精度无法分辨和识别储集体内部储层结构。在无井或井之外储集体连通性无法描述的条件下部署井位,导致同一连通单元钻井数量过多,或钻井直接命中主体规模性储集体概率低,增加大型酸压作业导致勘探开发成本增加,制约了超深碳酸盐岩断控缝洞储集体油气藏高效勘探开发。针对现有碳酸盐岩断控储集体储层连通性识别描述方法应用范围存在的不足,提出了一种适用于超深领域无井区域的碳酸盐岩断控储集体储层连通性地震描述方法。首先应用地震最大似然属性及门槛值,结合属性井震标定或地质规律认识,通过三维雕刻获得断控储集体的空间轮廓。其次在断控储集体空间范围内通过地震均方根速度获取同一海拔深度任意两点的地层压力,比较这两点的压力差从而判断该两点之间储层是否具有连通性。这种利用同一个连通缝洞单元内同一深度地层压力相等原理描述储集体连通性的方法经生产验证是有效适用的,能够为其他地区相似地质目标的储层内部连通性判别提供可实施的技术流程和方法借鉴。

顺北超深断溶体储层典型试井曲线特征及类别

顺北地区超深断溶体储层主要发育有裂缝及片状洞穴,采用可横向穿越缝洞储集体的水平井进行开发,其试井曲线形态特征复杂多变。依据井筒和表皮效应结束后的中期试井曲线的典型特征,将顺北地区实测试井曲线分成了3个大类。该3大类试井曲线特征直接反映了井与缝洞储集体的不同接触关系。再根据后期的试井形态特征,将顺北地区实测试井曲线细分成了9个亚类,不同的亚类试井曲线特征明显不同,是井外围缝洞发育状况变化的试井曲线响应。最后,提出了与试井曲线特征相对应的3大类9个亚类的试井解释评价物理模型。本文研究成果可用于指导顺北地区的试井分析与试井研究工作,亦可为其他深层断溶体储层的试井研究提供借鉴与参考。

断溶体油藏井洞垂向窜流试井解释模型

断溶体油气藏储层类型多样,非均质性极强,常规多重孔隙介质模型以及简单溶洞等势体模型难以广泛应用。文中针对断溶体油藏复杂的地质特征,考虑大溶洞向井筒的垂向窜流以及小尺度缝洞储集体分别向井筒和大溶洞的径向供给作用,建立了双层双重孔隙介质井洞垂向窜流试井解释模型;利用Laplace变换方法获得井底压力解,绘制井底压力典型曲线并划分流动段,对窜流通道传导率、大溶洞半径、裂缝传导系数比等参数进行了敏感性分析。结果表明:窜流通道传导率主要影响早期窜流“下凹”特征,数值过大或过小均会导致早期窜流“下凹”特征减弱甚至消失;大溶洞半径与大溶洞储容比也主要影响早期窜流“下凹”特征,数值越大,“下凹”特征越明显;裂缝系统传导系数比和裂缝储容比主要影响中、晚期的窜流“下凹”特征。该研究结果对复杂断溶体油藏储集体参数评价具有重要意义。

洞式溢洪道与自然冲沟组合的泄洪消能结构设计优化研究

通过水力学计算和水工模型试验,研究了竹寿水库扩建工程侧堰洞式溢洪道与自然冲沟内设台阶的泄洪消能结构水力特性。研究发现:泄大流量时,洞式溢洪道侧堰泄流能力略小于理论计算值,理论计算拟定的消力池结构尺寸较合理,冲沟内消能台阶转弯段的反超坡度需大于设计初拟值,优化调整后的洞式溢洪道与消能台阶组合泄洪消能结构对流态的控制较好。

超深断控碳酸盐岩缝洞储集体地震预测与井轨迹设计——以顺北油田4号断裂带中北部为例

顺北断控缝洞型油气藏主要受走滑断裂控制,断裂带的活动强度控制了储层发育程度,储集空间主要为断裂破碎形成洞穴、孔洞、裂缝,储层的空间展布非均质性强,缝洞体的空间定位和量化表征是制约井位井型的选择和高效动用的关键。综合测井、地震、地质等资料对顺北4号带断裂北段碳酸盐岩储集体进行立体半定量化表征研究。结果表明,顺北碳酸盐岩储集体沿断裂带呈不规则分布,储集体纵向延伸大(高度50~800 m),沿断裂面非均质性强,走滑断裂带拉分段、平移段及挤压段不同分段的储集体规模、组成差异较明显。拉张段储集体体积空间最大,孔洞占比最高(35%)、裂缝(65%);平移段体积空间较小,洞穴占比较低(44%)、裂缝(56%)。并根据储层预测及储集体空间展布进行井轨迹分类设计,拉分段平面宽度较大、断裂面与储集体夹角在0~30°,采用垂向大斜度角顺穿断裂带,最大限度地钻遇储集体;平移段断面窄,储集规模小,断面与储集体夹角在30~50°,采用垂向中斜坡角斜穿断裂带,钻井揭示储集体长度相比横穿可提高1.8倍,实现高产稳产。上述技术方法取得了良好的钻探效果。

Seismic identification and characterization of complex storage space oil and gas reservoirs

To predict complex reservoir spaces(with developed caves,pores,and fractures),based on the results of full-azimuth depth migration processing,we adopted reverse weighted nonlinear inversion to improve the accuracy of porous reservoir prediction.Scattering imaging three-parameter wavelet transform technology was used to accurately predict small-scale cave bodies.The joint inversion method of velocity and amplitude anisotropy was developed to improve the accuracy of small and medium-sized fracture prediction.The results of multiscale fracture modeling and characterization,interwell connectivity analysis,and connection path prediction are consistent with the production condition.Finally,based on the above prediction findings,favorable reservoir development areas were predicted.The above ideas and strategies have great application value for the efficient exploration and development of complex storage space reservoirs and the optimization of high-yield well locations.

塔河油田奥陶系古岩溶洞穴充填物时代鉴别特征及其储集意义

洞穴充填物的充填时代分析能够帮助认识洞穴的形成过程、充填结构序列和储集空间发育规律。塔河油田奥陶系岩溶洞穴受到物理充填作用的显著影响,其充填物的时代鉴别特征及其对储集空间发育的影响缺乏系统的分析。基于塔河油田奥陶系地质背景、岩心、测井、测年及产能资料的分析,认为:(1)灰绿色层理构造钙质砂岩和泥质粉砂岩为搬运充填成因,与裂缝共生的灰绿色泥质粉砂岩为渗流充填成因,它们的充填时代为海西早期,杂色砾岩的砾石成分复杂,磨圆分选较好,颗粒支撑,也为搬运充填成因,但充填时代为加里东晚期;(2)角砾岩的角砾成分一致,磨圆分选差且被灰绿色渗流泥充填,为海西早期洞穴掩埋时垮塌充填的结果,无渗流泥充填的角砾岩,裂纹化且多含方解石或沥青,多发育在洞穴顶部,为深埋藏阶段垮塌作用的结果;(3)岩溶洞穴缝洞储集体控制因素十分复杂,洞穴掩埋期的搬运、渗流与垮塌作用多产生泥质充填,储集性差;深埋藏期垮塌作用,产生次级裂缝且无泥质充填,储集性好,洞穴顶部及上部为有利储层发育位置。本研究为岩溶洞穴形成过程和油气藏高效开发提供有价值的参考。

深层缝洞型碳酸盐岩储层水力裂缝扩展机理研究

为了准确掌握深层缝洞型碳酸盐岩油藏压裂过程中水力裂缝的扩展规律,基于弹性力学、断裂力学和流–固耦合理论,建立了适用于缝洞型储层的水力裂缝扩展数学模型,采用数值模拟方法分析了水力裂缝扩展过程与缝洞体的相互作用规律,并对“沿缝找体”压裂技术的适用性进行了深入探讨。数值模拟结果表明:溶洞周围发育天然裂缝时,会影响缝洞体周围局部诱导应力场,使水力裂缝更容易沟通缝洞体;采用大排量注入低黏压裂液或中小排量注入高黏压裂液,仅能沟通与水力裂缝初始扩展方向夹角较小的溶洞,而对与水力裂缝初始扩展方向夹角较大的溶洞,则需考虑采用强制转向技术进行沟通。研究结果表明,基于井眼与缝洞体的配置关系,采用“沿缝找体”压裂技术可以实现直接沟通、定向沟通和沿缝沟通3种缝洞体沟通模式,显著扩大储量动用范围。

一种缝洞型油藏井-缝-洞组合的生产数据分析模型

目前关于生产数据分析方法的研究主要集中于连续孔隙型砂岩油气藏。由于缝洞型油藏非均质性强,非连续特征明显,常规生产数据分析方法理论对其适用性较差。文中考虑了缝洞型油藏离散缝洞介质特征,并基于等势体溶洞模型思想,建立了缝洞型油藏井-缝-洞组合的生产数据分析模型,通过拉普拉斯变换求解得到归一化系数及井底压力解,并绘制得到了缝洞型油藏生产数据分析模型典型图版。结果表明:溶洞体积及储容能力的增大会减小规整化产量,使得规整化产量积分导数曲线下凹特征更明显;裂缝长度及横截面积的增加会增大规整化产量,使得曲线向上抬升。结合现场实测井的静动态资料,应用井-缝-洞模型进行计算分析发现,所建立的模型能够达到较好的图版拟合效果及压力历史拟合效果,验证了模型的可靠性,为缝洞型油藏日常生产数据利用、储层结构分析及储量评价提供了一种较为可靠的计算方法。

塔河油田西部斜坡TH10421井区中—下奥陶统迷宫型缝洞结构特征

为了明确塔河油田上奥陶统厚覆盖区TH10421高累产井区的古岩溶洞穴成因及缝洞结构关系,利用古地貌恢复、地震属性提取、缝洞体雕刻等方法,厘清研究区地表水系分布特征、断裂特征、洞穴空间结构,首次识别出塔河油田TH10421井区的缝洞系统为洪水成因迷宫型洞穴系统,并结合油藏动态生产特征分析迷宫型洞穴系统的缝洞体连通关系。研究结果表明:TH10421井区发育共轭型次级走滑断裂网络,网格状断裂为迷宫型洞穴提供初始溶蚀通道;加里东运动中期Ⅱ幕地表岩溶湖泊提供高流量岩溶水补给,岩溶水沿网格状断裂下渗注入一间房组形成迷宫型洞穴;岩溶水顺断裂的溶蚀表现为同时性、选择性特点,造成TH10421井区迷宫型洞穴在不同方向断裂和不同深度上的溶蚀程度差异较大,东部浅层洞穴管道的连通性好,西部浅层洞穴管道的连通性较差,深层缝洞的连通性好。

碳酸盐岩储集层岩溶洞穴垮塌的力学机制

为确定碳酸盐岩储集层岩溶洞穴的垮塌机理,利用应力场模拟技术,以岩溶洞穴正交二维剖面为基础,建立二维力学模型,模拟碳酸盐岩岩溶洞穴在负压状态下的应力分布;通过对控制变量进行多元线性回归,构建了岩溶洞穴垮塌预测模型,结合破裂临界点的应力函数,预测洞穴垮塌与应力、深度和宽度的关系。洞穴发生岩爆和垮塌的最主要影响因素是上覆地层压力、储集层抗压强度和抗弯强度。垂向分布的2个洞穴,垂直距离小于0.3倍洞穴半径时,洞穴隔板发生破裂,导致洞穴连通;在垮塌破裂过程中,洞穴高度变化较为明显,宽度变化较小。

塔河油田浅覆盖区中—下奥陶统承压岩溶缝洞结构特征——以T738井区为例

塔河油田浅覆盖区中—下奥陶统岩溶缝洞体发育,油气开发效果较好。受上奥陶统良里塔格组和隔水层的围限,浅覆盖区中—下奥陶统缝洞体的岩溶发育特征不同于受排泄基准面控制的裸露型岩溶和岩溶水深循环的埋藏型岩溶。为了明确塔河油田浅覆盖区T738井区中—下奥陶统的洞穴成因机理和岩溶缝洞结构,利用“残厚趋势组合法”恢复了海西早期浅覆盖区的古地貌、古水系,综合测井、地震等手段识别了隔水层、岩溶洞穴层,结合油藏动态生产特征构建了浅覆盖区承压岩溶条件下的缝洞结构模式。结果表明:①海西早期古地貌总体北东高、南西低,发育北东—南西走向浅切割型树枝状地表水系,北部裸露区提供高水力梯度、高流量的岩溶水补给;②T738井区处于半开放式承压岩溶环境,中—下奥陶统发育3套隔水层围限下的2套迷宫型岩溶缝洞系统;③受隔水层、水动力梯度、走滑断裂等因素影响,一间房组、鹰山组上段洞穴层具有纵向水动力联系,发育侧向-上升型、孤立型、侧向型和盲端型等4类承压岩溶缝洞结构。研究成果对塔河油田浅覆盖区T738井区的缝洞型油藏开发有重要地质指导意义。

塔北隆起跃满地区奥陶系一间房组缝洞型储层三维建模

塔北隆起跃满地区奥陶系一间房组缝洞型碳酸盐岩储层受到构造和岩溶双重影响,不同的储集体尺度及形态差异大,储层非均质性强。因此,准确地刻画研究区储集体的形态及储层的展布对研究区的勘探开发具有重要意义。在研究区储层特征及储层纵向发育规律认识的基础上,结合地震、测井等资料,基于“多尺度多类型”的总体建模思路对研究区进行了储层建模。针对溶洞储层,优选出对溶洞反应灵敏的“特征属性”,分析得到截断值,基于“特征属性”建立“训练图像”,以测井资料作为硬数据,溶洞发育概率体作为软数据约束,进行建模;通过对地震资料进行人工解释建立了大尺度裂缝模型,对中尺度裂缝采用蚂蚁追踪技术进行确定性建模,对小尺度裂缝利用裂缝密度拟合函数,以蚂蚁体为约束进行了随机建模。采用同位条件赋值法对多个模型进行了融合,建立了跃满地区一间房组缝洞型碳酸盐岩储层三维地质模型。

结构张量导向储层预测技术在LS地区的研究与应用

LS地区碳酸盐岩奥陶系目的层主要发育洞穴型、孔洞型和裂缝型3种类型储层,储层非均质性强,且储集规模受多期活动走滑断裂体系控制,断控储集体储层地震响应特征复杂多样,预测与描述难度大。在前期研究的基础上,从梯度结构张量、张量薄化、构造应力理论入手,对不同类型储层进行实际应用效果测试分析,逐步形成了梯度结构张量定断控储集体轮廓,张量薄化、结构张量约束波阻抗反演、构造应力等属性结合有效地进行区分预测孔洞缝不同类型储层,多属性融合雕刻技术描述断控储集体空间展布特征,在LS地区实际应用中证实了技术的有效性及适用性,有效指导了后期目标优选和钻井设计,对SB油田超深层断控缝洞体勘探开发具有重要意义。