Drilling fluid technology for horizontal wells to protect the formations in unconsolidated sandstone heavy oil reservoirs

Major factors that cause damage in drilling in unconsolidated sandstone heavy oil reservoirs include: invasion of solids in drilling fluid, incompatibility between the liquid phase of drilling fluid and crude oil, and hydration and expansion of reservoir clay minerals. Therefore, a solid-free weak gel drilling fluid system for horizontal wells to protect the formations was developed that contains seawater + 0.1%–0.2% NaOH + 0.2% Na2CO3+ 0.7% VIS + 2.0% FLO + 2.0% JLX, weighed with KCl or sodium formate. The drilling fluid system has unique rheological properties, temporally independent gel strength, and excellent lubricating and inhibition performance. It is compatible with formation fluids, it not only meets the needs of horizontal well drilling, but also effectively protects the reservoir. The technique is well performed in tens of horizontal wells in offshore oilfields, such as WC13-1, BZ34-1, NP35-2, and BZ25-1 oilfields.

摘要钻井过程中造成疏松砂岩稠油油藏发生损害的主要因素是：钻井液固相侵入、钻井液液相与原油不配伍及储集层黏土矿物水化膨胀。为此研制出适于疏松砂岩稠油油藏储集层保护的无固相弱凝胶水平井钻井液体系：海水+0.1%～0.2%NaOH+0.2%Na2CO3+0.7%VIS+2.0%FLO +2.0%JLX，用KCl或甲酸盐加重。该钻井液具有独特的流变性能，凝胶强度无时间依赖性，具有优异的润滑性能和抑制性，与储集层流体配伍性好，不仅能够满足水平井钻井作业需要，而且具有优异的储集层保护效果，经文昌13-1油田、渤中34-1油田、南堡35-2油田、渤中25-1油田等数十口海上油田水平井验证，效果良好。