Drilling Fluid Technology for Horizontal Wells in Ecuador Tambococha Oilfield
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摘要: 厄瓜多尔Tambococha油田由于钻遇松散且微裂缝发育的地层,钻进中井壁易垮塌;其目的层高孔高渗,易发生储层损害问题。为此,以聚合醇XCS-III和乳化石蜡G325为主剂,通过优选其他环保型处理剂,研制了强封堵储层保护水基钻井液。该钻井液利用乳化液滴、浊点效应、微米颗粒及刚性粒子等的协同封堵作用来降低油水界面张力,阻止钻井液进入地层,从而达到防塌封堵和保护储层的目的。室内试验表明,该钻井液抑制性较强,岩屑在其中的线性膨胀量与在清水中相比降低了64.8%;封堵性能好,其粒径分布与理想充填曲线能够较好拟合;储层损害小,对Napo组U层岩心平均伤害率10.25%;环保性能好,钻井液重金属含量等达到了污水排放标准要求。Tambococha油田的15口水平井应用了该钻井液,钻井过程中井眼稳定、起下钻顺畅,钻后平均单井日产原油超过300 t,产油量较邻井提高近90%,且钻井废液及钻屑环保指标均达到EPA1311排放标准要求。研究结果表明,该强封堵储层保护水基钻井液,能够满足厄瓜多尔Tambococha油田水平井钻井提速及储层保护技术需求。Abstract: The borehole wall sloughing easily happens during drilling due to the unconsolidated formation with micro-fracture development in Tambococha Oilfield, Ecuador. The target stratum is characterized by high porosity and high permeability, causing reservoir damage. For this reason, with polyalcohol XCS-III and emulsified paraffin G325 as the main agents, accompanied by optimized eco-friendly agents, water-base drilling fluid that would provide strong reservoir protection during plugging were studied. The drilling fluid utilized the synergistic plugging effect of emulsified droplets, cloud point effect, micron particles and rigid particles to reduce the oil-water interfacial tension. It prevented the drilling fluid from entering the formation, finally achieving anti-collapse plugging and reservoir protection. Laboratory experiments showed that the drilling fluid had strong inhibitory properties, reducing the linear expansion of cuttings by 64.8% compared with that in clean water. The plugging performance was good, and its particle size distribution was consistent with the ideal filling curve. The damage to the reservoir was minor with an average damage rate of 10.25% to the cores of Layer U in the Napo Formation. The drilling fluid was eco-friendly, and the content of heavy metals met the standards for sewage discharge. The drilling fluid system was successfully applied to 15 horizontal wells in Tambochocha Oilfield, achieving good wellbore stability and smooth tripping. The average daily crude oil output of a single well exceeded 300 t, which was nearly 90% higher than that of offset wells. Such envi-ronmental indicators as waste drilling fluid and drilling cuttings met the requirements of EPA1311 discharge standards. The research results showed that the water-base drilling fluid could meet the rate of penetration (ROP) improvement and reservoir protection requirements of horizontal wells in Tambococha Oilfield, Ecuador.
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Key words:
- horizontal well /
- drilling fluid /
- wellbore stability /
- reservoir protection /
- Tambococha Oilfield /
- Ecuador
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表 1 页岩在不同聚合醇溶液中的线性膨胀量
Table 1. Linear expansion of shale in different polyalcohol solutions
序号 样品 加量, % 线性膨胀量/(mm·h–1) 20 min 1 h 2 h 4 h 8 h 1 清水 0.70 1.03 1.43 1.93 2.55 2 PGSC-1 3 0.48 0.78 1.05 1.42 1.83 3 XCS-Ⅲ 3 0.30 0.55 0.78 1.12 1.53 4 聚丙二醇400 3 0.55 0.80 1.35 1.80 2.35 5 聚乙二醇6000 3 0.50 0.85 1.17 1.63 2.16 表 2 AKUA钻井液的基本性能
Table 2. Basic properties of AKUA drilling fluid
测定条件 漏斗黏度/s API滤失量/mL 塑性黏度/(mPa·s) 动切力/Pa 静切力/Pa 初切 终切 常温 45~70 5~7 15~25 10~25 2~4 4~10 100 ℃/16 h 35~55 3~5 10~20 7~18 1~3 2~8 注:钻井液密度为1.05~1.25 kg/L。 表 3 岩心反排试验结果
Table 3. Test results of core flowback
岩心编号 原始渗透率/mD 反向渗透率/mD 突破压力/MPa 反排压力/MPa 岩心伤害率,% 反排时间/min 1# 735.58 643.72 0.15 0.17 12.49 30 2# 793.33 720.23 0.14 0.15 9.21 30 3# 814.86 741.02 0.11 0.12 9.06 30 表 4 现场钻井废液检验结果
Table 4. Test results of well site waste drilling fluids
参数 pH值 电导率/(μS·cm–1) 固体悬浮物含量/(mg·L–1) 化学需氧量/(mg·L–1) 总烃/(mg·L–1) 重金属含量/(mg·L–1) 钡 铅 钒 总铬 排放标准 5.0~9.0 <2 500 <1 700 <120 <20 <5.0 <0.5 <1.0 <0.5 检测结果 8.4 295 527.58 13.88 0.06 0.3 0.15 0.4 0.1 表 5 现场钻屑检验结果
Table 5. Test results of well site drilling cuttings
参数 pH值 电导率/(μS·cm–1) 总烃/(mg·L–1) 重金属含量/(mg·L–1) 钡 铅 钒 总铬 排放标准 6.0~9.0 <4 000 <1.0 <0.05 <1.0 <0.2 <5.0 检测结果 7.4 2 350 0.8 <0.000 5 0.001 7 0.009 2 0.4 -
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