含煤层系相控型致密气储层非均质性评价的沉积要素与甜点预测策略:以鄂尔多斯盆地为例

doi:10.13745/j.esf.sf.2025.7.16

摘要/Abstract

摘要：

全球油气勘探实践已表明,致密气是当前最重要、也是今后最具前景的非常规油气资源。致密气特别是致密砂(砾)岩气富集的沉积环境主要为河流-三角洲与滨岸,而这些沉积环境与含煤层系有千丝万缕的成因关系。含煤层系可划分出两大类源-储组合关系,常常形成煤层气、致密气及常规天然气共存的资源格局,其中富砂质的沉积相控型致密气常具有大面积、连续分布的特征,但其内部非均质性强,导致甜点储层预测难;而砂泥间互型与泥包砂型致密气储层规模的确定是甜点预测的难点。通过鄂尔多斯盆地典型区块的实例分析表明:含煤层系的沉积环境与相带变迁、砂体沉积成因类型、沉积构型的差异以及优势骨架砂体的分布是造成此类致密气储层的成岩差异、储层非均质性的关键沉积因素。而含煤层系致密气储层的甜点预测首先应注重井震结合、采用相控预测方法;把沉积与成岩充分结合起来,以沉积相带约束成岩相带划分;注意合理评估含煤层系致密储层原生孔隙的损失量,并通过成因砂体对比明确砂体连通性。进行致密气储层综合评价与含气规模预测时,要注意不同评价方案的差异性;在含气储量计算时,注意规避容积法在取参方面的不准确性,而采用地质统计学的方法取参并计算储量更适用。另外,在相控地质建模时,由于致密气储层非均质性强,也要注意进行合理物性截断取值。

关键词: 含煤层系, 相控型致密气储层, 源-储组合, 储层非均质性, 甜点预测

Abstract:

Global petroleum exploration practice has shown that tight gas is the most important and promising unconventional resource currently. Sedimentary environments enriched in tight gas, particularly tight sandstone and conglomerate gas, are primarily fluvial-deltaic and lacustrine shoreline systems, which exhibit an inextricable genetic link to coal-bearing intervals. Within these coal-bearing intervals, two primary source-reservoir assemblages are recognized, commonly resulting in a resource configuration where coalbed methane, tight gas, and conventional natural gas coexist. Tight gas reservoirs within sandy sedimentary facies typically exhibit extensive lateral distribution but strong internal heterogeneity, posing significant challenges for sweet spot prediction. Predicting the size and geometry of tight gas reservoirs characterized by interbedded sand and mud, and mud-encased sand bodies, remains a key challenge in sweet spot prediction. Analysis of typical blocks in the Ordos Basin demonstrates that sedimentary environment and facies belt variations within coal-bearing intervals, differences in sand body genetic types and sedimentary architecture, and the distribution of dominant framework sand bodies are key sedimentary factors controlling the diagenetic differences and reservoir heterogeneity in such tight gas reservoirs. Sweet spot prediction for tight gas reservoirs in coal-bearing intervals should emphasize the following: First, integrate well and seismic data utilizing sedimentary facies-constrained prediction methods. Second, combine sedimentation and diagenesis studies to constrain the delineation of diagenetic facies belts using sedimentary facies belts. Third, accurately assess primary porosity loss in tight reservoirs of coal-bearing intervals and clarify sand body connectivity through genetic sand body correlation. When conducting comprehensive evaluation and predicting gas-bearing potential, it is essential to be aware of potential discrepancies arising from different evaluation schemes. For calculating gas reserves/gas-in-place (GIP), the parameter uncertainty inherent in the volumetric method should be considered, whereas geostatistical methods offer a more robust approach to parameter estimation and reserve calculation. Additionally, in sedimentary facies-controlled geological modeling of tight gas reservoirs, the strong heterogeneity necessitates the selection of reasonable petrophysical cutoff values.

Key words: coal-bearing intervals, sedimentary facies controlled tight gas reservoir, assemblage of source rock and reservoir, reservoir heterogeneity, sweet spot prediction

中图分类号:

P618.130.21

李胜利, 张亚雄, 于兴河, 付超, 马喜斌. 含煤层系相控型致密气储层非均质性评价的沉积要素与甜点预测策略:以鄂尔多斯盆地为例[J]. 地学前缘, 2025, 32(5): 389-403.

LI Shengli, ZHANG Yaxiong, YU Xinghe, FU Chao, MA Xibin. Sedimentary elements of heterogeneity evaluation and sweet spot prediction strategies on sedimentary facies controlled tight gas reservoirs in coal-bearing intervals: Examples from the Ordos Basin[J]. Earth Science Frontiers, 2025, 32(5): 389-403.

图/表 10

表1 含煤层系源-储组合关系对致密气储层与含气性的影响

Table 1 Impacts of source rock and reservoir assemblage on gas bearing property in coal bearing tight gas reservoirs

源-储组合类型		源-储关系		煤系影响		储层结构		含气特点		典型实例
	源-储相互分离型		下生上储为主		煤系主要为气源,对储层质量影响较小		富砂稳定型为主,也有泥包砂型与砂泥互层型		典型致密气,大面积连续分布为主,但丰度低		鄂尔多斯盆地下石盒子组、松辽盆地营城组、四川盆地沙溪庙组、库车坳陷巴什基奇克组
	源-储叠置混存型		自生自储, 源-储叠置		煤系不仅为气源,还对储层质量影响较大		泥包砂型与砂泥互层型为主,也有富砂稳定型		致密气与煤层气间互,或致密气、煤层气、页岩气“三气”共存,规模变化大		鄂尔多斯盆地太原组—山西组、松辽盆地沙河子组、四川盆地须家河组、库车坳陷阿合组、鹤岗盆地城子河组、吐哈盆地水西沟群

图1 鄂尔多斯盆地东南缘山西组—下石盒子组五段层序划分

Fig.1 Sequence division from Shanxi Formation to the fifth member of the Lower Shihezi Formation in the southeastern part of the Ordos Basin

图2 鄂尔多斯盆地东南缘山西组—下石盒子组五段不同层序的沉积模式

Fig.2 Sedimentary facies patterns of different sequences from Shanxi Formation to the fifth member of the Lower Shihezi Formation in the southeastern part of the Ordos Basin

图3 鄂尔多斯盆地东南缘山西组—下石盒子组五段岩性组合样式 GR—自然伽玛;DEN—密度。

Fig.3 Lithological assemblages from Shanxi Formation to the fifth member of the Lower Shihezi Formation in the southeastern part of the Ordos Basin

图4 鄂尔多斯盆地东南缘Xf8井山西组—盒八段不同沉积环境的砂体类型及其储层物性岩性符号见图3的图例说明;GR—自然伽玛;DEN—密度;LLD—深侧向电阻率。

Fig.4 Sand body types and physical properties of different sedimentary environments from Shanxi Formation to 8th member of the Lower Shihezi Formation in Well Xf8, the southeastern part of the Ordos Basin

图5 辫状河主要构型单元的叠置模式其中a-a’、c-c’、d-d’3种砂体叠置关系连通性最好;b-b’这种砂体叠置方式易在心滩坝与河道侧积层之间出现侧积泥,而可能形成封堵条件;e-e’与f-f’两种类型连通性最差,这是由于废弃河道的泥塞作用而形成的。而心滩坝内部的落淤层因其不够稳定,对连通性的影响有限。注意顺流方向与横切水流方向的沉积方式存在差异,横切水流方向的储层连通性差异性更明显。

Fig.5 Superposition patterns of major architecture units of braided river

表2 苏里格南区盒八段成岩储集相划分(据文献[29]修改)

Table 2 Diagenetic reservoir facies of 8th member of the Lower Shihezi Formation in the southern block of Sulige gas field. Modified after [29].

成岩相	沉积微相	粒度	孔隙类型	成岩特征
弱压实- 长石溶蚀相	心滩、河道、河漫砂	中—粗粒,粗粒	大量粒间溶孔、铸模孔、晶间溶孔	长石、部分岩屑溶蚀严重, 基底胶结
绿泥石胶结- 弱长石溶蚀相	河道、水下分流河道、河口坝、河漫砂	中粒,中—细粒	部分粒间溶孔, 少量晶间溶孔孔	绿泥石胶结,长石溶蚀较弱, 孔隙胶结
硅质- 碳酸盐胶结相	分流间湾、泛滥平原、漫溢砂	细粒—极细粒	微裂缝发育, 少量溶孔	硅质—碳酸盐胶结发育, 颗粒线—凹凸接触
致密成岩相	分流间湾、漫溢砂	细粒—极细粒	微裂缝少量	胶结作用、压实作用强烈, 颗粒凹凸接触

图6 鄂尔多斯盆地富县地区盒八段的成岩相分析图

Fig.6 Diagenetic reservoir facies distribution map of 8th member of the Lower Shihezi Formation in the Fuxian block of the Ordos Basin

图7 动静结合的河道带与河道砂体对比示例图(据文献[45]修改)

Fig.7 An example of channel belt and channel correlation integrated static geological study with production performance. Modified after [45].

图8 鄂尔多斯盆地苏里格南区盒八段X2小层致密气储层综合评价结果示例图 a—渗透率为主因子的储层综合评价结果;b—饱和度为主因子的储层综合评价结果。

Fig.8 Different tight gas reservoir evaluation results on X2 layer of 8th member of the Lower Shihezi Formation in the southeastern part of the Ordos Basin

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