抗高温无固相弱凝胶钻井完井液技术

针对委内瑞拉西部BARUA区块产层泥砂岩互层多,砂岩胶结不充分,地层松散、易塌易漏、地温梯度高以及Barua区块油藏物性较差,产收率低的问题,为了保持井壁稳定、减少表皮污染,通过室内实验研究了BH-ELASTICOHTHP体系。该体系按照“流体套管技术”理念,利用体系高黏度特点,配合白云质碳酸钙有效封堵产层孔喉,稳定井壁和降低表皮污染;利用低剪切速率黏度高的特点实现井底净化和钻屑返出;该体系还具有抗高温、抗腐蚀性强、主剂材料易降解等优点,适用于低密度、低渗、成岩性差的地层。MGB-0066井现场试验应用表明,BH-ELASTICO-HTHP体系防漏防塌能力强,对储层和环境保护性好,该井产量超过邻井产量30%以上,达到了安全钻井和提高油井产量的双重目的。BH-ELASTICO-HTHP体系的“流体套管技术”理念也为老油田及低油藏物性油田的增产增收指出了方向。 

High Temperature Solid Free Water Base Drill-in Fluid

The reservoir formations in the Block Barua, west Venezuela, are characteristic of multiple interbedded mudstones and sandstones, unconsolidated sandstones because of poor cementation, borehole wall collapse and frequent mud losses, high temperatures and poor reservoir physical properties. A drilling fluid named BH-ELASTICO-HTHP has been developed based on the "fluid casing concept" to try to maintain borehole stability during drilling and to minimize skin contamination of the reservoir formations. The BHELASTICO- HTHP drilling fluid has high viscosity and low gel strengths, and can be used to stabilize borehole wall and reduce skin factors when treated with dolomitic CaCO3 as a temporary plugging agent. The low-shear-rate viscosity of the BH-ELASTICO-HTHP drilling fluid helps clean the borehole. As a high temperature drilling fluid formulation, with its main additives easy to degrade, this drilling fluid is suitable for use in drilling formations with low pore pressure, low permeability, and unconsolidated formations. The application of this drilling fluid in the well MGB-0066 demonstrates that the BH-ELASTICO-HTHP drilling fluid has strong mud loss controlling capacity and shale inhibitive capacity; it helps protect reservoir formations from being damaged and is environmentally friendly. The well MGB-0066 has actual oil production rate 30%more than that of the offset well. The use of the BH-ELASTICOHTHP drilling fluid realized safe drilling and enhanced production. The "fluid casing concept" will help in designing drilling fluid formulations for use in old oilfield or in reservoirs with poor physical properties.