欠平衡水平井王平1井饱和盐水水包油钻井液技术

Drilling the underbalanced horizontal well WP-1 using oil-in-water saturated brine system

王平1井是江汉油田的第一口中曲率水平井,储层岩性为盐间非砂岩层,水平井段采用欠平衡钻井技术。该井钻井液技术难点为:抑制岩盐析出,防止井径扩大;井身设计为“马鞍”型,且靶区共有5个靶点,使得钻柱与井壁的接触更加紧密,摩阻与粘附力增大;大斜度井段和水平段的携岩问题和井眼的清洁问题较为突出;如何降低饱和盐水钻井液的密度,满足欠平衡钻井施工的要求,保护好油气层,是该井能否钻探成功的关键。应用结果表明,饱和盐水水包油钻井液有效地抑制了盐岩层的溶解和坍塌,保证了井眼轨迹的平滑,而且钻井液润滑性能好,起下钻、电测和下套管作业均畅通无阻;由于应用了新型处理剂PMPH,保证了钻井液具有较高的切力,增强了悬浮和携带岩屑的能力,避免了岩屑床的形成;钻井液密度始终在1.35-1.51 g/cm3范围内,满足了欠平衡钻井对密度的要求。王平1井投产后初产量为65t/d,稳产量为12.2 t/d。

Well WP-1 is the first medium radius horizontal well drilled in Jianghan oilfield, and its horizontal interval is drilled using under-balanced technology. Salt beds exist in the reservoir, thus salt precipitation and hole enlargement must be controlled. As a saddle profile is adopted for hole configuration, and there are as many as 5 targets in the target area, this makes a tight contact between drill pipe and borehole and leads to high friction and adsorption. The cuttings transportation and hole cleaning in the high deviated hole and horizontal interval is also a serious problem. Thus proper drilling fluid technology must be applied, and it is the key for the success of this well. Applications show that the oil in water saturated brine system can effectively control the caving-in and sloughing of salt beds, and ensures a regular hole trajectory. Moreover, because of its good lubricity, such operations as tripping, logging and casing running can be smoothly carried out. The use of new mud additive PMPH ensures the high shearing rate of drilling fluid, and enhances the suspension and cuttings carrying capacity, which avoids the forming of cutting beds. The drilling fluid density is controlled within 1. 35 g/cm3 to 1. 51 g/cm3, and this can meet the requirements of under-balanced drilling. The initial production rate reaches as high as 65 t/d, and its stable production is 12. 2 t/d.