Study on integrated evaluation system of tight oil geological engineering: a case study of Chang 8 reservoir in western Ganquan area, Ordos Basin
Received date: 2024-04-16
Online published: 2025-03-13
Copyright
The integration of geological engineering is one of the key technologies for efficient development of tight oil, and plays a very important role in the development of tight oil in Chang 8 member of the lower Yanchang Formation in West Ganquan. However, the evaluation criteria for geological and engineering sweet spots have not yet been formed in this block, which restricts the deployment of future oil and gas exploration and development plans. Therefore, using logging data to identify reservoirs in Chang 8 member of the study area, the evaluation index system of geological sweet spot is formed in terms of source rock, diagenetic facies and reservoir distribution characteristics. From brittleness index, rock stress and strain test, rock tensile fracture test, the evaluation index of engineering sweet area is established. The results show that: (1) The identification accuracy of reservoir fluid properties of Chang 8 member in the study area can reach 90% by differential analysis and fluid sensitive parameter method; (2) An evaluation index of geological sweet spot area of tight oil reservoir is established based on sand thickness, reservoir thickness, sedimentary facies, porosity, diagenetic facies and TOC*H parameters; (3) On the basis of petrophysical experiments and actual construction results, the evaluation indexes of the sweet spot of Chang 8 tight reservoir engineering in the study area are established from the aspects of petrophysical parameters and the optimization of differentiated fine-cut volumetric fracturing process. Under the constraint of geological sweet spot and engineering sweet spot, the recovery rate of Class Ⅰ reservoir can be increased from 5.3% to 17.3%, Class Ⅱ reservoir can only be increased from 4.86% to 8.19%, and Class Ⅲ reservoir can only be increased from 2.81% to 4.95% by optimizing fracturing process parameters.
LianRu YANG , JinFeng LI , JiJi SUN , Qian WANG , YanJun WU , YinHui REN . Study on integrated evaluation system of tight oil geological engineering: a case study of Chang 8 reservoir in western Ganquan area, Ordos Basin[J]. Progress in Geophysics, 2025 , 40(1) : 166 -175 . DOI: 10.6038/pg2025II0024
表1 长8段不同成岩相测井参数响应范围Table 1 Response range of logging parameters of different diagenetic facies in Chang 8 member |
| 成岩相 | GR/API | SP/mV | AC/(μm/s) | RILD/(Ω·m) |
|---|---|---|---|---|
| 中压实不稳定组分溶蚀溶孔相 | ||||
| 强压实钙质胶结致密相 | ||||
| 强压实高岭石胶结致密相 | ||||
| 强压实致密成岩相 |
表2 甘泉西部地区“地质甜点区”划分标准Table 2 Classification criteria of "geological dessert area" in western Ganquan |
| 有利区类型 | 砂厚/m | 油层/m | 沉积相 | 孔隙度/% | 成岩相 | TOC*H |
|---|---|---|---|---|---|---|
| Ⅰ类 | ≥20 | ≥6 | 水下分流河道 | ≥8 | 中压实不稳定组分溶蚀溶孔相 | ≥100 |
| Ⅱ类 | 15~20 | ≥4 | 水下分流河道 | 7~9 | 中压实不稳定组分溶蚀溶孔相 | 50~100 |
| 15~20 | ≥2.5 | 水下分流河道及侧翼、浊积水道 | ≥7 | 强压实高岭石胶结致密相 | ≥100 | |
| Ⅲ类 | < 15 | ≤2.5 | 浊积水道前缘、水下分流河道及侧翼 | ≤8 | 强压实钙质胶结致密相、强压实致密成岩相 | ≥50 |
表3 拉伸实验结果(李锦锋等,2022)Table 3 Tensile test results(Li et al., 2022) |
| 序号 | 试件直径/mm | 试件高/mm | 破坏荷载/kN | 拉伸强度/MPa |
|---|---|---|---|---|
| 1 | 50.3 | 25.1 | 16.44 | 7.94 |
| 2 | 50.1 | 24.7 | 22.12 | 5.02 |
| 3 | 49.8 | 25 | 15.07 | 5.92 |
| 4 | 50.3 | 24.9 | 24.65 | 9.9 |
| 5 | 49.8 | 25.2 | 23.91 | 10.91 |
| 6 | 50.2 | 25.3 | 21.99 | 7.15 |
| 7 | 49.7 | 25.3 | 18.02 | 5.63 |
| 8 | 50.2 | 24.8 | 17.84 | 7.32 |
| 9 | 49.8 | 25 | 14.8 | 9.82 |
| 10 | 50.2 | 24.8 | 16.32 | 5.9 |
表4 甘泉西部地区“工程甜点区”划分标准及压裂优化Table 4 Division standard of "engineering sweet spot" and optimization of fracturing parameters in west Ganquan area |
| 有利区类型 | 岩石物理参数 | 差异化细切割体积压裂工艺优化 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 脆性/% | 泊松比 | 杨氏模量 | 段间距/簇 | 入液强度/(m3/m) | 单段支撑剂用量/m3 | 裂缝半长/m | 裂缝间距/m | 缝高/m | 改造段数/段 | 支撑剂类型 | 水平段长度/m | 井间距/m | ||
| Ⅰ类 | ≥42 | < 0.20 | >30 | 4~6 | 15~20 | 20~25 | 185 | 15 | 17.2 | 16 | 石英砂,20/40目为50%, 40/70目和100/140为50% | 1200~1500 | 350~400 | |
| Ⅱ类 | 40~42 | 0.2~0.25 | 20~30 | 4~5 | 10~15 | 16~22 | 150 | 22 | 13.6 | 11 | ||||
| Ⅲ类 | < 40 | >0.25 | < 20 | 3~4 | 5~10 | 14~18 | 143 | 25 | 8.6 | 7 | ||||
感谢延安大学石油工程与环境工程学院在论文完成中提供分析测试条件, 感谢审稿专家提出的修改意见.
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