基于成岩储集相定量分类模式确定特低渗透相对优质储层——以AS油田长6_1特低渗透储层成岩储集相定量评价为例

Based on the Quantitative Classification Mode of Diagenetic Reservoir Facies to Filter Relatively Excellent Quality:Taking the quantitative assessment of diagenetic facies of Chang 6_1 reservoir of AS oilfield hyposmosis reservoirs for an example

针对陕北斜坡中部特低渗透储层受沉积环境、成岩作用及构造等因素影响,成岩过程压实和胶结作用强烈,储层储集性能和渗流结构差异大的特点。利用AS油田长61特低渗透储层成岩储集相定量分类模式圈定相对优质储层,分别进行了区块长61砂岩的成岩作用和孔隙演化分析,建立了不同类别成岩储集相定量分类模式与综合评价指标体系。不同类型成岩储集相成岩过程参数演化及其储集、渗流特征明显不同。Ⅰ、Ⅱ类成岩储集相压实孔隙损失率30.0%～38.1%;胶结孔隙损失率30.1%～36.0%;溶蚀次生孔隙度增加达9.7%,平均溶蚀增加孔隙度都在5.1%～6.5%。它们在低孔、特低渗储层成岩过程中压实、胶结损失孔隙相对较少,溶蚀增加孔隙较多,成为定量评价该区长61特低渗透相对优质储层的成岩储集相"甜点"标准。选用区块各井长61样品物性分析及储集空间鉴定结果,沿成岩过程进行孔隙演化分析推演,得出区块长61各类井成岩阶段孔隙演化参数。分别利用压实损失孔隙度、胶结损失孔隙度、溶蚀增加孔隙度、孔隙度、渗透率及面孔率等特征性参数,通过灰色理论集成,进行被评价参数与评价指标的矩阵分析、标准化、标准指标绝对差的极值加权组合放大及综合归一分析处理,综合成岩过程中参数演化定量分析的多种信息,筛选出Ⅰ、Ⅱ类成岩储集相"甜点"。它们主要分布在酸源的湖盆中心下伏烃源岩(生油区)附近,处于三角洲前缘多期水下分流河道叠置部位的有利储集砂体中,成岩过程中压实、胶结损失孔隙度较小,在其有机酸性水形成时期保留了较多原生孔隙,酸性水容易进入并溶解其中易溶的碎屑颗粒及胶结物,次生浊沸石和长石溶蚀孔隙发育,形成了该区长61特低渗透储层中含油有利区的相对优质储层。通过上述筛选的优质储层确定出该区湖盆中心向南西方向含油有利区连片的规模和范围,圈定出该区沉积作用、成岩作用、后期构造作用及流体改造作用形成的有利成岩储集成因单元,有效地反映出该区特低渗储层中相对优质储层形成的地质特点,进一步表征了该区特低渗透储层含油有利区的分布规律、延伸方向及非均质性特征。从而,提高了该区储层沉积、成岩特征及其含油有利区分布的认识,为特低渗透油田增储上产提供了有利目标和井区。

The reservoir in Shannbei structural slope is affected by the depositional environment,diagenesis and structural factor,so the compaction and cementation effects are intense in Shanbei slope center.In this paper relative high quality reservoirs of hyposmosis reservoir were filtered,in which diagenetic reservior facies mode of quantitative classification of Chang 61 reservoir in AS oilfield of extra-low permeability was used.With the work of sandstone diagenesis and porosity evolution analysis of Chang 61,different types of diagenetic reservoir facies model of quantitative classification and comprehensive evaluation index system of diagenesis reservoir facies was established.The evolution parameter of diagenesis in different diagenetic reservior facies and the characteristic of reservoir ＆ flow are obviously not the same.The compaction porosity loss rate of I,II diagenetic reservior facies is 5.1%6.6%;cement prosity loss rate is 30.1%36.0%;dissolution of secondary porosity increased up to 9.7% with an average of increasing porosity of 5.1%6.5%.It can be the standard of diagenetic reservior facies ＂dessert＂ because of less loss of pore compaction cementation and great increase of dissolution porosity.And these can be used to quantitatively evaluate reservior. Diagenetic stage of pore evolution parameter of different wells in Chang 61 could get by the results’ deduction of pore evolution analysis along diagenetic process,and the results come from the material analysis and the identification of pore space of different samples in Chang 61.Though the integration of gray theory of the following parameters,compaction loss porosity,cementation loss porosity,dissolution increased porosity,porosity,permeability and thin section porosity,the matrix analysis of evaluation parameters and evaluation indicator can be normalized,the absolute difference extreme of standard indicators could be weighted combination ＆ amplification and integrated analysis and processing.With the integration of multiple information in diagenesis,theⅠ,Ⅱtype diagenesis reservoir facies ＂dessert＂ was filtered.They mainly distributed in the vicinity of generating rock of the centre of acidic lake basin,and were located in favorable reservoir sand in overlying location of the underwater distributary channel of delta front sub-facies,more primary porosity was remained in the formation of organic acids water period in diagenetic process,diffluent clastic particles and cementing material were dissolved by acidic water,secondary laumontite and feldspar pore was generated.Thus,relative high-quality reservoirs which controlled and blocked out favorable oil-bearing areas in extra-low permeability Chang 61 reservoir were formed. The scale and scope of favorable oil field with the direction from the center to the southwest in the lake area could be identified by the above mentioned high-quality reservoir.Using sedimentation,diagenesis,post-tectonic and the role of fluid transformation draw the scope of favorable diagenetic reservoir unit,the geological features of high-quality reservoir could be reflect,and with a further characterization of the distribution pattern,extend the direction and characteristics of non-homogeneous in this low permeability oil field.Thus,the awareness of reservoir sedimentation,diagenesis features and the distribution of favorable oil area was raised,which is benefit to extra-low permeability oil field to reach a high output.