Study on gas-water characteristics and gas-bearing properties of Upper Paleozoic Shan23-He8 member reservoir in middle area of Jingbian Gas Field
Received date: 2024-03-27
Online published: 2025-03-13
Copyright
In order to clarify the Nuclear Magnetic Resonance(NMR) characteristics and influencing factors of gas-water layer of He8 member in southeast Sulige of Ordos Basin, two-dimensional NMR technology was used to characterize the gas-water layer characteristics, combined with the analysis results of formation water, reservoir physical properties, formation anisotropy and gas supply, the NMR response characteristics of the gas-water layer of He8 member in the study area were clarified. The relationship between formation water, pore type, pore throat structure, formation anisotropy, gas supply and reservoir gas bearing is analyzed. The results show that: ①The formation water in the study area is mainly CaCl2 type, but the salinity difference is strong, and the distribution is 3669~325000 mg/L. The water type is all CaCl2, the pH value is 4.21~8.98, and it is weakly acidic.[r(Na+)/r(Cl-)] was less than 0.61, the coefficient of chloride to magnesium[r(Cl-)/r(Mg2+)] was greater than 7.0, and the coefficient of magnesium to calcium[r(Mg2+)/r(Both Ca2+)] are less than 0.69, and the metamorphic coefficients[r(Cl--Na+)/r(Mg2+)] are more than 0.47, indicating that the formation water is in a relatively stagnant reduction state, the formation is strongly sealed, and the natural gas is well preserved. ②The distribution of gas-water layers in He8 member in the study area is complex, and two-dimensional nuclear magnetic resonance technology can effectively distinguish the gas-water layers. ③The pore types of the reservoir in He8 member are mainly residual intergranular pores and feldspar solution pores, with porosity ranging from 2.70% to 14.48% and permeability ranging from 0.04 to 15.92×10-3 μm2. The reservoir physical properties affect the gas bearing properties of the reservoir, and the porosity and permeability of the reservoir are greater than 7.0% and 0.2×10-3 μm2, respectively. The porosity and permeability of the gas-bearing and differential gas layers are 5%~9.5% and (0.02~0.7)×10-3 μm2, respectively, while the porosity and permeability of the dry layer are less than 5% and 0.1×10-3 μm2, respectively. The anisotropy of the gas layer is between 15%~20%, and that of the dry layer is less than 6%.
XingGuan CHENG , ZiWei ZHANG , Nan CHEN , YanBin ZHANG , ZiAng MENG , XiaoLi ZHANG , YaJun LI , GaoRun ZHONG . Study on gas-water characteristics and gas-bearing properties of Upper Paleozoic Shan23-He8 member reservoir in middle area of Jingbian Gas Field[J]. Progress in Geophysics, 2025 , 40(1) : 176 -187 . DOI: 10.6038/pg2025HH0517
表1 地层水化学参数表征的地质意义Table 1 Geological significance of formation water chemical parameter characterization |
| 地层水参数 | 地质意义 |
|---|---|
| 地层水离子浓度 | 反映地层水动力特征和水化学环境,在一定程度上可表征油气的保存和破坏条件. |
| 钠氯系数 [r(Na+)/r(Cl-)] | 反映地层水的浓缩变质作用程度和地层水文地球化学环境.钠氯比大于0.85为流动水特征,钠氯比小于0.50则为停滞环境(胡绪龙等,2008;杨仁超等,2022). |
| 脱硫系数 [r(SO42-)/r(Cl-)] | 脱硫系数小于1.0的地层水,通常表明地层水还原彻底,埋藏于封闭良好的地区.反之,则认为还原不彻底,可能受浅表层氧化作用的影响. |
| 氯镁系数 [r(Cl-)/r(Mg2+)] | 氯镁系数越大,反映地层水封闭性越好、封闭时间越长,浓缩变质作用越深,有利于油气的聚集和保存.含气区地层水氯镁系数值一般大于5. |
| 碳酸盐平衡系数 [r(HCO3-+rCO32-)/r(Ca2+)] | 越靠近油气藏,油气性质越轻,碳酸盐平衡系数值越小. |
| 镁钙系数 [r(Mg2+)/r(Ca2+)] | 低的镁钙系数值与次生孔隙的发育有关.镁钙系数越大,浓缩变质程度就越大,油田水封闭就越好,有利于油气聚集与保存. |
| 变质系数 [r(Cl--Na+)/r(Mg2+)] | 系数越大,表明封闭程度好,水—岩作用强,该系数为负值时,表明可能受到大气降水的影响. |
表2 山23-盒8地层水化学特征综合统计表Table 2 Comprehensive statistical table of chemical characteristics of formation water under Shan23-He8 |
| 层位 | 水型 | 矿化度/(mg/L) | 变质系数 | 钠氯系数 | 脱硫系数 | 镁钙系数 | 氯镁系数 | 碳酸盐平衡系数 |
|---|---|---|---|---|---|---|---|---|
| 盒8下1 | CaCl2 | 9313~289870(79238) | 0.8643~1.9769 | 0.0186~0.4627 | 0~0.9260 | 0~0.4250 | 7.762~151.939 | 0~0.5637 |
| 盒8下2 | CaCl2 | 8463~324946(73444) | 0.4728~1.9769 | 0.0000~0.6073 | 0~3.49 | 0~0.6998 | 4.600~333.600 | 0~1.3286 |
| 山23 | CaCl2 | 3669~234391(71663) | 0.6160~1.3720 | 0.0101~0.6073 | 0~6.65 | 0~0.6065 | 7.64~333.64 | 0~0.8099 |
图1 T1-T2二维图谱识别流体性质理论图版(石玉江等,2023)Fig 1 T1-T2 two-dimensional spectrum Identification of fluid properties (Shi et al., 2023) |
感谢审稿专家提出的修改意见和编辑部的大力支持!
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