Formulation Design of Drilling Fluid Loss Control and Plugging Strategies in Deepwater Subsalt Reservoirs
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摘要: 全球范围内的盐下油气资源十分丰富,其中巴西深水海域有着丰富的油气资源。Mero油田属于典型的深水盐下油气资源,位于巴西东南部海域桑托斯盆地,储层埋深>5000 m,上覆盐膏层150~3000 m,盐下储层主要为下白垩统BVE和ITP组碳酸盐岩。Mero油田的Mero3区块漏失情况最为严重,漏失总量达17 105 m3。通过地质资料和钻井资料分析了漏失的主要原因,包括断层和天然裂缝的发育、地层薄弱以及地层的强非均质性,这些因素共同导致了封堵层承压能力差,易发生反复漏失。本研究收集了Mero油田常用的堵漏材料,开展了粒度分布、摩擦系数、抗压能力、配伍性等性能评价实验,建立了堵漏材料性能参数数据库,并优选出了适用于深水盐下储层防漏堵漏作业的高性能堵漏材料。基于不同漏失速度根据高效架桥和致密填充的设计方法设计了三套防漏堵漏配方,并细化了防漏堵漏配方的应用流程。同时,提出了精细调控钻井工艺和坚持防漏堵漏结合的策略,在易漏地层加强井筒ECD的精细控制,降低井下正压差,减少诱导裂缝的产生。研究成果在Mero3区块NW8井现场堵漏施工中取得了显著效果,针对不同漏失速度的情况,均能够有效减缓漏失速度,为巴西Mero油田乃至其他类似盐下储层的油气开发提供有效的技术支持,促进安全、高效的油气资源开采。Abstract: Subsalt oil and gas resources are abundant worldwide, with significant reserves located in the deepwater offshore regions of Brazil. The Mero field is a typical example of deepwater subsalt oil and gas resources, located in the southeastern Santos Basin offshore Brazil. The reservoir depth exceeds 5000 meters, with an overlying salt gypsum layer ranging from 150 to 3000 meters. The subsalt reservoirs are primarily composed of Lower Cretaceous BVE and ITP carbonate rocks. The Mero3 block in the Mero field experiences the most severe lost circulation, with a total loss of 17,105 m3. Through geological and drilling data analysis, the main causes of lost circulation were identified, including the development of faults and natural fractures, weak formation layers, and the strong heterogeneity of the formation. These factors collectively result in poor pressure-bearing capacity of the sealing layer, leading to repeated lost circulation incidents. This study collected commonly used plugging materials in the Mero field and conducted performance evaluation experiments on particle size distribution, friction coefficient, compressive strength, and compatibility. A database of plugging material performance parameters was established, and high-performance plugging materials suitable for deepwater subsalt reservoir loss prevention and plugging operations were selected. Based on different loss rates, three loss prevention formulas were designed using efficient bridging and dense filling methods, and the application process for these formulas was refined. Furthermore, a strategy for fine-tuning drilling techniques and maintaining a combination of loss prevention and plugging was proposed. This strategy includes strengthening the precise control of the wellbore ECD in loss-prone formations, reducing downhole overpressure, and minimizing the occurrence of induced fractures. The research results achieved significant success in the field plugging operations at the NW8 well of the Mero3 block. In cases with varying loss rates, the plugging strategy effectively slowed down the loss rate. This provides valuable technical support for the oil and gas development of Brazil's Mero field and other similar subsalt reservoirs, promoting the safe and efficient extraction of oil and gas resources.
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图 1 巴西桑托斯盆地盐下构造分区与油气田分布[8]
表 1 Mero3区块漏失情况统计
井号 漏失次数/次 漏失量/m3 漏失损失时间/h NW2A 2 4544.7 80 NW8 4 4873.7 52.5 NW12 2 953.7 36 表 2 堵漏材料粒度分析结果
材料编号 D90/μm D 50/μm D 10/μm LCM-D1 4504.32 3884.16 3412.18 LCM-D2 3716.66 3330.27 2950.67 LCM-D3 4363.41 3384.59 182.15 LCM-D4 3223.02 2338.17 1915.56 LCM-D5 2149.92 1702.28 1420.45 LCM-E1 388.714 209.634 41.137 LCM-E2 219.350 49.009 6.689 LCM-F1 1348.690 570.433 48.578 LCM-F2 6043.26 3576.25 1940.85 表 3 堵漏材料摩擦系数评价指标
摩擦系数 μ≤0.5 0.5<μ≤0.8 0.8<μ≤1.1 1.1<μ≤1.4 μ>1.4 摩擦系数级别 低 中等偏低 中等 中等偏高 高 表 4 堵漏材料摩擦系数评价结果
材料名称 最大静
摩擦系数最大动
摩擦系数平均动
摩擦系数摩擦系数
级别LCM-D1 1.02 1.40 1.15 中等偏高 LCM-D2 1.16 1.42 1.13 中等偏高 LCM-D3 1.34 2.01 1.23 中等偏高 LCM-D4 2.64 2.77 1.47 高 LCM-D5 2.36 2.39 1.51 高 LCM-E1 0.97 1.20 0.95 中等 LCM-E2 1.94 1.94 1.38 中等偏高 LCM-F1 1.31 1.45 1.20 中等偏高 LCM-F2 0.78 0.85 0.72 中等偏低 LCM-G1 0.94 0.98 0.85 中等 LCM-G2 0.91 0.97 0.89 中等 LCM-G3 1.00 1.01 0.92 中等 表 6 堵漏材料抗压能力评价结果
材料名称 D90降级率/% 抗压能力级别 LCM-D1 −5.31 中等偏高 LCM-D2 −1.32 高 LCM-D3 4.14 高 LCM-D4 28.75 中等偏低 LCM-D5 21.33 中等偏低 LCM-F1 17.04 中等 LCM-F2 12.34 中等 表 7 堵漏材料配伍性评价标准
SF SF≤0.51 0.51<SF≤0.52 0.52<SF≤0.53 0.53<SF≤0.54 SF>0.54 配伍性 好 中等偏好 中等 中等偏差 差 表 5 堵漏材料抗压能力评价标准
D90降级率/% D DR﹥30 20< D DR≤30 10< D DR≤20 5< D DR≤10 D DR≤5 抗压能力 低 中等偏低 中等 中等偏高 高 表 8 堵漏材料配伍性评价实验结果
材料 静置不同时间后的静态沉降因子 配伍性级别 1 h 2 h 4 h 8 h LCM-D1 0.5277 0.5299 0.5309 0.5342 中等偏差 LCM-D2 0.5261 0.5260 0.5293 0.5299 中等 LCM-D3 0.5174 0.5167 0.5173 0.5201 中等 LCM-D4 0.5246 0.5251 0.5256 0.5274 中等 LCM-D5 0.5387 0.5397 0.5422 0.5412 差 LCM-E1 0.5267 0.5291 0.5299 0.5302 中等偏差 LCM-E2 0.5061 0.5047 0.5060 0.5078 好 LCM-F1 0.5079 0.5088 0.5123 0.5151 中等偏好 LCM-F2 0.5097 0.5255 0.5261 0.5261 中等 表 9 纤维类堵漏材料分散能力评价标准
分散系数F /% F≤20 20<F≤40 40<F≤60 60<F≤80 F>80 分散性能 低 中等偏低 中等 中等偏高 高 表 10 纤维类堵漏材料分散能力评价结果
材料 不同质量加量在蒸馏水中
分散系数/%1.0%质量加量在不同浓度CMC中
分散系数/%分散能力级别 0.5% 1.0% 1.5% 0.5% 1.0% 1.5% LCM-G1 92.86 95.71 98.57 95.71 100 100 高 LCM-G2 10.00 18.57 24.29 18.57 24.29 77.14 中等偏高 LCM-G3 7.14 8.57 17.14 8.57 25.71 31.43 中等偏低 表 11 堵漏材料酸溶率评价标准
酸溶率/% RA≤20 20<RA≤40 40<RA≤60 60<RA≤80 RA>80 酸溶率级别 低 中等偏低 中等 中等偏高 高 表 12 酸溶率测试实验结果
材料 酸溶率/% 酸溶级别 土酸 盐酸 LCM-D1 86.41 90.14 高 LCM-D2 82.21 87.35 高 LCM-D3 8.65 18.11 低 LCM-D4 100 100 高 LCM-D5 100 100 高 LCM-E1 44.91 65.27 中等偏高 LCM-E2 43.39 62.34 中等偏高 LCM-F1 55.84 73.74 中等偏高 LCM-F2 16.76 26.53 中等偏低 LCM-G1 2.52 7.23 低 LCM-G2 67.09 79.31 中等偏高 LCM-G3 26.71 41.3 中等 表 13 堵漏材料性能参数数据库
材料名称 D90/μm 摩擦系数 抗压能力 配伍性 分散能力 酸溶率 LCM-D1 4504.32 中等偏高 中等偏高 中等偏差 -- 高 LCM-D2 3716.66 中等偏高 高 中等 -- 高 LCM-D3 4363.41 中等偏高 高 中等 -- 低 LCM-D4 3223.02 高 中等偏低 中等 -- 高 LCM-D5 2149.92 高 中等偏低 差 -- 高 LCM-E1 388.714 中等 -- 中等偏差 -- 中等偏高 LCM-E2 219.350 中等偏高 -- 好 -- 中等偏高 LCM-F1 1348.690 中等偏高 中等 中等偏好 -- 中等偏高 LCM-F2 6043.26 中等偏低 中等 中等 -- 中等偏低 LCM-G1 -- 中等 -- -- 高 低 LCM-G2 -- 中等 -- -- 中等偏高 中等偏高 LCM-G3 -- 中等 -- -- 中等偏低 中等 表 14 堵漏浆设计结果
配方 堵漏浆配方 承压能力/MPa 1# 基浆+4 % LCM-D5 + 2.5 % LCM-F1+ 2 % LCM-E2 + 0.6 % LCM-G2 12.24 2# 基浆+5 % LCM-D4 + 3 % LCM-F1 + 3 % LCM-E2 + 0.6 % LCM-G2 10.33 3# 基浆+2 % LCM-D1+5 % LCM-D5+3 % LCM-F1 +3 % LCM-E2+0.6 % LCM-G2 10.45 -
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