渤中沙河街水平井安全钻井及储层保护

Safe drilling of horizontal wells and reservoir protection in Shahejie Formation, Bozhong Block

针对下第三系储层开发的水平井,依靠现有的弱凝胶钻井液技术无法满足安全钻井和储层保护的要求,根据沙河街地层特点,通过改变配方中甲酸钾与KCl的加放比例,降低钻井液活度,促使储层段钻井液与沙河街地层活度相匹配。利用甲酸钾离子压缩黏土胶体颗粒双电层的能力,提高了对泥页岩的抑制性;储层保护方面采用逐级拟合填充技术,即通过优选CaCO_3粒径的大小与地层孔喉粒径相匹配达到封堵作用;完井期间使用隐形酸作为破胶剂,达到解堵效果,从而解决沙河街地层易发生井壁失稳和深部地层储层保护难度大等技术难题。该技术在BZ34-7-A2H井中成功应用,实现了安全钻井与储层保护的目的。

For horizontal wells drilled for development of Tertiary reservoirs, conventional weak gel drilling fluid may not fully satisfy all demands for drilling safety and reservoir protection. With consideration of specific properties of Shahejie Formation, proportions of potassium formate and KCl used in the formula have been modified to reduce the activity of the drilling fluid with the intent to match the drilling fluid used in reservoir formation with the activity of the Shahejie Formation. By utilizing capacities of potassium formate ions in compression of double electric layers in clay gel particles, inhibition performances to the mud shale can be enhanced effectively; To protect reservoir formations, step-by-step matching and filling have been adopted by selecting Ca CO3 grains with optimal sizes to achieve perfect match with pore diameters in reservoir formation. Duirng completion, recessive acid can be used as gel breaker to obtain desirable unplugging performances and effectively remove problems related to sidewall instability and proper protection of deep formation in the Shahejie Formation. The innovative technique has been applied successfully in Well BZ34-7-A2 H to achieve goals in safe drilling and reservoir protection.