A Well Productivity Model for Multi-Layered Marine and Continental Transitional Reservoirs with Complex Fracture Networks

Using the typical characteristics of multi-layered marine and continental transitional gas reservoirs as a basis,a model is developed to predict the related well production rate.This model relies on the fractal theory of tortuous capillary bundles and can take into account multiple gas flow mechanisms at the micrometer and nanometer scales,as well as the flow characteristics in different types of thin layers(tight sandstone gas,shale gas,and coalbed gas).Moreover,a source-sink function concept and a pressure drop superposition principle are utilized to introduce a coupled flow model in the reservoir.A semi-analytical solution for the production rate is obtained using a matrix iteration method.A specific well is selected for fitting dynamic production data,and the calculation results show that the tight sandstone has the highest gas production per unit thickness compared with the other types of reservoirs.Moreover,desorption and diffusion of coalbed gas and shale gas can significantly contribute to gas production,and the daily production of these two gases decreases rapidly with decreasing reservoir pressure.Interestingly,the gas production from fractures exhibits an approximately U-shaped distribution,indicating the need to optimize the spacing between clusters during hydraulic fracturing to reduce the area of overlapping fracture control.The coal matrix water saturation significantly affects the coalbed gas production,with higher water saturation leading to lower production.

Theoretical Study on Quantitative Characterization of Interlayer Interference in Multi-Layer Commingled Production

X oilfield is a typical layered reservoir with a large vertical span and many oil-bearing formations. There are significant differences in reservoir types and fluid properties among various formations. The interlayer interference is severe in the development process. At present, the interlayer interference research based on dynamic monitoring data cannot meet development adjustment needs. Combined with the field test results, through the indoor physical simulation experiment method, dynamic inversion method, and reservoir engineering method, this paper analyzes the main control factors and interference mechanism of interlayer interference, studies the variation law of interference coefficient, improves and forms the quantitative characteristic Theory of interlayer interference in multi-layer commingled production, and provides theoretical guidance for the total adjustment of the middle strata division in the oilfield.

Quantitative Characterization and Dynamic Law of Interlayer Interference for Multilayer Commingled Production in Heavy Oil Reservoirs by Numerical Simulation

This paper moves one step forward to build?a?numerical model to research quantitative characterization and dynamic law for interlayer interference factor (IIF) in the multilayer reservoir which was heavy oil reservoirs and produced by directional wells. There are mainly four contributions of this paper to the existing body of literature. Firstly, an equivalent simulation method of the pseudo start pressure gradient (PSPG) is developed to quantitatively predict the value of?IIF?under different geological reservoir conditions. Secondly, the interlayer interference is extended in time, and the time period of the study extends from a water cut stage to the whole process from the oil well open to produce?a?high water cut. Thirdly, besides the conventional productivity interlayer interference factor (PIIF), a new parameter, that is, the oil recovery interlayer interference factor (RIIF) is put forward.?RIIF?can be used to evaluate the technical indexes of stratified development and multilayer co-production effectively. Fourthly,?the?effectsof various geological reservoir parameters such as reservoir permeability and crude oil viscosity, etc. on the?PIIF?and?RIIF’s?type curves?are?discussed in detail and the typical plate?is?plotted. The research results provide a foundation for the effective development of multilayer heavy oil reservoirs.

The application of gas chromatography fingerprint technique to calculating oil production allocation of single layer in the commingled well

Gas chromatography fingerprint technique has the advantages of fast performance and low cost. It can be used to conduct analysis without interruption either in the field or at laboratory. This technique has been used successfully in such cases that conventional production logging techniques are powerless. Taking low-concentration anthracene as internal standard, we calculated the absolute concentrations!of fingerprints, initially made some experiments directly on biodegradation of crude oils, and calculated production allocation in the Gudong Oil field. Compared with the production logging, this method has made up for the deficiencies of the former GC fingerprint technique. It will find wide applications in monitoring the trend of production in various oil-fields.

Calculating single layer production contribution of heavy oil commingled wells by analysis of aromatic parameters in whole-oil GC-MS

Traditional fluid production profile logging is not usually suitable for heavy-viscous crude oil wells.Biodegradation of heavy oil can lead to the loss of n-alkanes,and the use of chromatogram fingerprint techniques in studying the production contributions of single layers in heavy oil commingled wells has limitations.However,aromatic compounds are relatively well preserved.We took the heavy oil commingled wells of small layers NG55 and NG61 in the ninth area of the Gudong oil field as examples.Based on the principle of chromatography,the whole-oil GC-MS was used,and the aromatic parameters which have a strongly linear relationship with the ratio of mixed two end member oils were verified and selected in laboratory.Studies showed that the ratio of （1,4,6-＋ 2,3,6-trimethylnaphthalene） to 1,2,5-trimethylnaphthalene has a strongly linear relationship with the ratio of the mixed two end member oils （R2=0.992）.The oil contributions from single layers NG55 and NG61 in six commingled heavy oil wells were calculated using established charts and this relationship.The calculated results are consistent with the results of long period dynamic monitoring and logging interpretation in the study area and can provide a scientific basis for monitoring production performance and hierarchical management of reservoirs.The study provides a new geochemical method for calculation of the contributions of single layers in heavy oil commingled wells when conventional fluid production profile logging is not suitable.

A dynamic evaluation technique for assessing gas output from coal seams during commingling production within a coalbed methane well: a case study from the Qinshui Basin

Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds.Permanent damage can result if this is not the case,especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output.Current theoretical models and measuring devices are inapplicable to commingled CBM drainage,however,and so large errors in predictive models cannot always be avoided.The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit.A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study.This technique comprises a downhole measurement system combined with a theoretical calculation model.Gas output parameters(i.e.,gas-phase flow rate,temperature,pressure)are measured in this approach via a downhole measurement system;substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit.Trends in gas output from a single well or each seam can therefore be predicted.The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15%and therefore conform with field use requirements.

Optimization methods of production layer combination for coalbed methane development in multi-coal seams

Based on the productivity equation of coalbed methane(CBM) wells, three indexes, main production layer optimization index, main production layer expansion index and capacity contribution index are proposed, with which the three-step optimization method of production-layer combination is established. In selecting main production layer, the coal seam thickness, CBM content, coal seam permeability, coal seam reservoir pressure and coal structure are considered comprehensively to evaluate the potential of the production layer. In selecting expansion of the main production layer combination, on the premise of ensuring full and slow desorption of the main production layer and non-exposure of the main production layer out of liquid surface, the degree of mutual interference between the main and non-main production layers is comprehensively evaluated by coupling the critical desorption pressure, layer spacing and reservoir pressure gradient difference. In optimizing production layer combination, the main concern is the economic efficiency of the combined layers. Only when the contribution coefficient of the main production layer is greater than 30% and the contribution index of the other production layers is more than 10%, the economic benefit of a CBM well after being put into production can be ensured. Based on the comparative analysis of the development effect of the development test wells in Songhe of Guizhou province, it is proved that the "three-step method" for the optimization of production-layer combination is scientific and practical, and can be used to design the multi-layer commingling scheme of coalbed methane.

CLEAN PRODUCTION AND SMELTING REDUCTION TECHNOLOGY

Clean Production is the best method for iron-steel making industry to eliminate pollution thoroughly. In order to achieve this object, smelting reduction technology should play the key role. Furthermore, process integration method can be used to solve the problem of residual gas utilization by integrating smelting reduction process with direct reduced iron unit, gasoline, methanol or dimethyl ether synthesis unit, etc. A new smelting reduction process has been proposed which can be constructed on the present plant site. Since this process can directly treat the lump coal and iron ore fines, it reduces st6ps necessary in traditional blast furnace process and Corex smelting reduction process.

Calculation of the contribution of single-zone production by ultraviolet spectrum technique:A case study in well QHD32-6-3 field

Based on the established mathematic model and graphic interpretation, a new method, which is used to calculate the contribution of single-zone production in a commingled producing well by the ultraviolet spectrum technique, has been established. The standard plate was drawn using the extinction coefficient E of sample oils formulated artificially as y-axis and the wavelength as x-axis. The curve resulting from the UV analysis of sample oils in the commingled well was inserted into the standard plate and compared. The proportion of each single zone in the commingled producing well was identical with the proportion of the curve which is closest to the curve of sample oils formulated artificially. In the well QHD32-6-3 field, taking well A22 for example and using this method, the production contribution of a single zone was calculated. The result showed that the Nm4 zone is a major "contributor", the proportion of the Nm4 zone is 70%, and that of the Nm1 zone is 30%. The ultraviolet spectrum technique provided a new reservoir geochemical technique of monitoring production contribution, especially for biodegraded heavy oil, but it has some limitation, just depending on the GC fingerprint technique.

基于双循环的气井产量劈分方法及应用

产量劈分系数是多层合采气藏动态预测的基础,建立产量劈分系数动态跟踪计算方法具有重要意义.基于产量劈分的物理意义,明确了产量劈分系数的求解关键参数为泄气半径,但泄气半径在实际应用中通常未知.结合产能方程和物质平衡方程,建立了闭环的产量劈分系数计算模型,计算模型包含泄气半径、平均地层压力和产量劈分系数等三个未知参数,为求解计算模型提出了双循环计算法,内循环求解泄气半径,外循环求解产量劈分系数,内循环和外循环均存在唯一解,循环规则包括正向递归和反向递归,内循环与外循环的循环规则始终相反,通过设定循环步长和误差上限,建立了双循环的计算流程,外循环包含内循环,内循环收敛时外循环才能进行,外循环决定了内循环能否收敛.数值模拟验证显示,产量劈分系数在不同产层、不同阶段、不同时间表现出不同的变化规律,双循环计算法不仅机理正确且精度很高.产气剖面对比显示,双循环计算法在现场应用中亦具有可靠的精度.双循环计算法属于三元方程组的求解方法,实现了产量劈分系数、泄气半径和平均地层压力的同时计算.

地面井分层卸压的煤系气合采原理及方式探讨

为了进一步认识制约煤系气合采的因素,提高煤系合层排采各产层的产气贡献,分别从动力、通道和气源条件出发,分析了煤系气合采的必备因素。基于改变地应力状态提高储层导流能力以及分层改变储层流体压力,满足多层合采动力条件的原理,提出了地面井分层卸压的煤系气合采方式。该方式通过在地面进行定向钻井,在目标储层中进行高压水射流作业,人工创造卸压空间(缝、槽、穴等),改变地应力状态,降低有效应力伤害,增加储层导流通道的数量和开度,提高目标储层压降传递速率。待储层压力降至符合煤系气合采动力条件时进行合层排采,从而提高煤系合采各产气层的产气贡献。相较于常规增产改造措施,此方式能够减少煤系气储层在有效应力作用下的储层伤害,且有助于提高储层压降传递效率,增强煤系气的解吸和扩散,降低多层煤系气合采过程中的层间干扰。在以上研究基础上,认为地面井分层卸压的合采方式主要适用于储层地应力大、产层间距小的煤系气储层,且有望在薄互层煤系气储层增产改造及层间干扰严重的叠合共生煤系储层开发领域进行应用推广。

东胜气田致密高含水气藏合采气井效果评价及产出影响因素分析

为了确定鄂尔多斯盆地北缘致密高含水气藏合采气井开发效果,指导同类型气藏合采气井高效开发。以东胜气田致密高含水气藏为研究对象,分析了单采井与合采井不同开发阶段、不同井区及纵向上的产出效果,以及合采井层间含气性差异对合采井产出的影响,明确了东胜气田致密高含水气藏合采井的开发效果及层间产出的影响因素。研究结果表明:①东胜气田致密高含水气藏合采井具有初期压力高、产量高的特征,但整体开发效果与气藏含气性或产水情况有相关性;②通过参数对比分析,合采井生产层产出效果与产层物性、含气性具有明显的正相关性,产层之间的含气性差异也会影响合采开发效果;③合采井稳定生产临界携液(携泡)流量与气井水气比也具有一定的相关性。结论认为:①东胜气田致密高含水气藏合采井初期压力、产量较高,但在低含气饱和度(高水气比)区域合采井整体开发效果较差,同时气田合采井随着开发时间的推移纵向上层间的产出状况也不断发生变化;②合采气井生产层物性、含气性越好,生产层的产出效果越好,且以物性条件为主导,但在较大的层间含气性差异下,合采井层间易发生严重的气液倒灌使得整体开发效果变差;③合采气井水气比越高,稳定生产临界携液(携泡)流量越大。

双层合采油井盲管控水机理数值模拟

依托胜利油田盲管控水先导开发试验项目,根据双层合采油井油水流入动态特征,建立了双层合采油井盲管控水模型,并利用Fluent软件开展不同长度与不同位置盲管作用下的双层合采油井地层产液特征数值模拟研究。结果表明:盲管可以增加高含水层的井底流压,降低地层产液流量。对于综合含水率达到80%的双层合采油井,盲管长度是影响其控水效果的主要因素,盲管越长,控水效果越明显。与无盲管相比,在2 m的高含水层全段放置盲管,产液含水率可降低30百分点。盲管位置是影响其控水效果的次要因素,在2 m的高含水层不同位置放置0.5 m盲管,产液含水率下降约3百分点。为保障控水效果,应针对高含水层所在位置,放置适应地层厚度的盲管,调控双层合采油井产液流量,达到控水的目的。在优化双层合采油井盲管长度和盲管位置的基础上,利用流体数值模拟对盲管的控水机理进行了深入研究,研究结果能为高含水油藏双层或多层合采油井实施盲管控水开采提供技术指导。

多层合采油藏层间非均质性表征研究

大井段多层合采开发往往面临严重的层间干扰问题,准确描述层间非均质性是解决层间干扰问题的关键。洛伦兹方法是描述层间非均质性最常用的手段,但其在开发领域适用性尚不明确。针对这一问题,运用数值模拟方法及油藏工程理论开展洛伦兹方法开发适用性研究。研究发现:洛伦兹方法表征非均质性与开发效果相关性不强,仅在局部敏感区间内对开发效果产生剧烈影响;同时,当洛伦兹系数相等时,曲线形状对开发效果也有影响,但传统方法无法有效表征。因此,对洛伦兹方法进行了修正,并对修正方法开展了物理模拟实验及油田数据验证。实验结果表明:修正后大大扩展了洛伦兹系数的敏感区间,使得水驱开发效果与洛伦兹系数之间的相关性显著增强。实例应用表明:修正前后,KL-A区洛伦兹系数与采收率相关系数从0.48增至0.87,KL-B区相关系数从0.74增至0.87,可见层间非均质性与开发指标的相关性显著增强。

煤层气藏相对渗透率动态计算方法研究

为获取煤层气藏气水相对渗透率实际变化特征,进一步深化对煤层气藏气水产出规律的认知,构建了结合煤层气藏实时动用情况的煤层气藏相对渗透率动态计算方法。该方法首先通过多煤层全过程耦合流动模型对目标单煤层或多煤层进行产量历史拟合,获得储层和流体的基本物性参数。而后,基于得到的基本物性参数开展煤层气井全生产周期产能预测,同时,根据储层压降漏斗的实时扩展规律对储层参数进行平均化处理,并结合流体的实际运移情况计算煤层气藏气—水相对渗透率曲线。研究结果表明:本文提出的煤层气藏相对渗透率动态计算方法可在对煤层气藏内部动用情况实时定量分析的基础上,动态计算煤层气藏实际气水相对渗透率。通过本文提出的方法计算得到的气相相对渗透率曲线上存在反转点,其反应储层中的解吸气开始稳定、连续的供应。若不考虑储层压降漏斗实际扩展规律,对储层参数进行全域平均,计算得到的煤层气藏气水相对渗透率将偏低。对于多煤层气藏,窜流效应导致的层间流体质量交换和储层压力下降不可忽略,生产3 y时气相窜流量与产气量比值可达0.57,水相窜流量与产水量的比值可达0.69。忽略窜流量条件下计算得到的煤层气藏气水相对渗透率偏低,仅为考虑窜流量条件下的42.89%和24.40%。在煤层气井实际生产过程中,含水饱和度保持在较高值,大于40%,受高含水饱和度的制约,煤层气藏气相相对渗透率值较低,小于0.2。

致密气藏多层砂体合采井产量递减分析方法

致密气藏主力产层多为多层叠置河道砂体,合采时普遍存在各产层贡献不明及砂体动用边界不清的问题。首先,考虑各层河道砂体形态特征和边界尺寸差异,根据等效渗流体积原则,建立了致密气藏多层河道砂体合采井生产模型。其次,基于现代产量递减分析理论,形成了致密气藏多层河道砂体的边界确定方法和合采井产量递减分析图版。最后,讨论不同河道砂体边界距离、砂体数量和砂体位置下的产量递减特征,明确了多层河道砂体对产量递减的影响。研究表明:致密气藏多层河道砂体合采井产量具有5个递减阶段,不稳定流中期阶段可诊断各层砂体边界距离是否相等;河道砂体范围越小,宽砂体数量越少,宽砂体占比越小,储集层稳产能力越差,不稳定流早期阶段和不稳定流中期阶段易出现产量递减速率增大现象。建立的产量递减分析方法可为产层动用程度评价和增产措施制定提供依据。

集束连续管井口悬挂分流装置的研究与应用

集束连续管作为油气生产管柱,利用自身多通道独立工作的特点,可以开展两气合采生产作业,实现同一口井多储层高效开采,尤其对储层物性差异大的地层开发优势显著。针对现有常规井口大通径管柱悬挂配套复杂、适用范围受限、同时需兼顾导流及密封的问题,采用多瓣式卡瓦悬挂结构,配合专用分流组件,研制了一种基于集束连续管两气合采工艺的井口装置。该装置具备井口悬挂和分流密封功能,解决了集束连续管2根内管与四通阀旁通中心基准面方向不一致的难题。室内试验和现场应用结果表明:集束连续管悬挂分流装置可以完成规定的测试内容,能够实现集束连续管在井口的悬挂和分流道控制,满足现场应用的要求。研究结果可为两气合采完井提供可行性保证施工的安全性,有助于完善集束连续管两气合采工艺的应用和推广。

薄—中厚煤层群煤层气井高产的地质与工程协同控制技术——以贵州织纳煤田文家坝区块为例

中国西南地区煤层气资源量十分丰富,且主要赋存于上二叠统煤系薄—中厚煤层群中,贵州地区虽然有近10年的煤层气规模化试采与探采工程实践,但仍存在低产井、低效井比例偏高的问题。为了推进贵州地区薄—中厚煤层群煤层气高效探采工作,在系统梳理织纳煤田文家坝区块地质条件、煤储层特征、开发工艺与开发效果基础上,分析了煤层气井高产及井间产气差异的地质控制因素,探讨了地质适配性分层压裂与合层排采技术。研究结果表明:①薄—中厚煤层群具有埋藏浅、含气性好、渗透率较高、储层压力欠压—正常的特征;②煤层气井高产既受阿弓向斜轴部构造应力集中、水力封堵作用下煤层气富集影响,同时也与浅埋藏条件下煤储层原始渗透性较高有密切关系,区内断裂构造与水文地质条件共同导致了丛式井组内井间产气效果差异;③应根据丛式井压裂煤层靶点间距及导水断层距离合理控制水力压裂施工规模,注前置液造缝阶段快速提升注入排量并非连续段塞增大裂缝延伸长度,注携砂液支撑阶段阶梯式连续加砂有效支撑裂缝;(4)长期维持小于0.5 MPa的低套压合层排采条件,缩短憋压持续时间,延长提产持续时间以提高稳产前的压裂液返排率,保证排采过程连续性以避免储层伤害,产气量提升阶段主动缓慢暴露上部产层。结论认为,文家坝区块具备煤层气探采的有利储层条件,浅埋藏背景下的煤储层特征及井区构造、水文条件共同影响到煤层气井的产气表现,选择与煤储层特征相匹配的分层水力压裂、合层排采工艺对提高煤层气采收率具有促进作用。

多层致密油气藏分层压裂井裂缝非均匀导流能力试井分析方法

压裂直井和多级压裂水平井是致密油气藏目前研究的主要井型,鲜有研究多层致密油气藏分层压裂井合采时非均匀导流能力裂缝参数解释问题。针对多层致密油气藏分层压裂工艺,摒弃致密储层传统压裂缝导流能力均匀的假设,考虑分层压裂缝扩展差异性引起的压裂缝导流能力不均匀现象,通过Laplace空间变换、Duhamel叠加原理和Stehfest数值反演方法,建立了具有非均匀导流能力压裂缝的多层致密油气藏分层压裂试井分析模型,研制了识别多层致密油气藏分层压裂井流动特征的试井分析图版,分析了井筒储集系数、裂缝表皮系数、压裂缝导流能力分布特征、储层物性等对油气渗流规律的影响。结果表明:多层致密油气藏分层压裂储层的油气渗流可分为5个阶段,早期流动阶段受井筒储集系数和裂缝表皮系数影响,中期流动阶段受压裂缝长度及导流能力控制;在相同生产压差下,增大各层压裂缝长度和导流能力有利于提高油气井产量;忽略压裂缝导流能力和压裂缝扩展的非均匀现象,将低估压裂缝区域压力损耗、高估压裂生产井早期产能。通过实例井试井解释,获取了各层裂缝参数。

煤层气井两层合采气水同产井底流压计算方法

井底流压是确定煤层气井合理工作制度,进而实现长期稳产的关键影响因素。针对定质量模型不考虑储集层段加速度压降和不同井段质量变化导致不符合两层合采特性,以及采用下部储集层井底流压作为2个储集层井底流压来调节生产制度导致不符合上部储集层调节需求的问题,对加速度压降表达式进行了分解和推导,建立了其与单位长度径向流量的关系式,推导了含径向流入的储集层段压降公式;将储集层分成多个微元段,建立了每个微元段的压降计算方法;根据各井段气水流量,推导了相应的气相和水相速度计算方程;将上述方程结合,建立了变质量模型。将生产数据分别代入变质量模型和定质量模型,气水同产时,变质量模型的误差为2.96%~6.67%,定质量模型的误差为7.33%~15.10%,变质量模型更加准确。2个储集层的井底流压相差较大,最大相差47.3%,因此需要根据各自的井底流压调节生产制度。变质量模型能够准确给出合采各层的井底流压,更符合现场实际,同时也避免了采用相同井底流压导致无法精准调节2个储集层生产制度的问题,从而为制定最优化排采制度、实现高产稳产提供技术支撑。