地层自生弱酸解堵技术在安塞低渗透油田的应用

Reservoir Blockage Relieving by Using in-Situ Self-Generating Weak Acid at Low Permeability Reservoirs in Ansai

本文报道的地层自生弱酸解堵液由稀盐酸、表面活性剂、聚合物及碱组成,按双液法工艺注入,前二组分为A液,后二组分为B液。实验考察了产CO2气,反应热升温及表面活性剂的降压作用,指出了盐酸和碳酸的酸化和硫酸盐垢转变为碳酸盐垢的作用。用清水、污水配制的溶液,反应升温、生成气体量及沉淀量大体相同。在被严重污染的岩心中,在46℃下注入A、B两液两个循环段塞共0.5 PV,测得注入压力逐渐下降。2004年8月在低渗透的安塞油田两口注水井,以盐酸浓度不同(15%和8%)、隔离液不同(2和3 m3)的注入工艺实施地层自生弱酸解堵,共注入3个循环段塞,一口井施工完全失败,注不进水,另一口井油套压均下降,注水量大增,有效期为40天。2005年10月按成功井例的施工工艺,即盐酸浓度大,隔离液量小,A、B量小,交替次数多,在另外两口注水井施工,均获得降压增注的效果,但有效期仍不长(40、35天)。图3表4参3。

The reservoir blockage relieving（removing） agent presented for stimulating water injection wells comprises dilute hydrochloric acid, surfactant, polymer, and alkaline and is applied by using a bi-fluid process of injection with fluid A composed of the former two and fluid B--the later two chemicals above mentioned. The gaseous CO2 generation, the temperature raise brought about by exothermic reaction, and the pressure drop in cores caused by surfactant injected were investigated experimentally and the acid etching and the conversion of sulfates by alkaline were stated. The temperature raise, CO2 reaction, and deposition of precipitates were similar with the test fluids prepared in a fresh or a produced water. A gradual decrease in injecting pressure was observed in the course of injecting fluids A and B alternatively in two cycles in volume of 0.5 PV totally into a severely contaminated core. Aug 2004, two water injection wells at Ausai tow permeability reservoirs were treated for relieving formation blockages by using the in-situ self-generated weak acid from fluids A and B injected alternatively in three cycles with slightly varying technologic parameters, hydrochloric acid concentration 15% or 8% and volume of spacer fluid 2 or 3 ms and the treatment in one well was hilured without any watertake and was successful in another, in which both tubing and casing pressures decreased and watertake rose significantly in a time duration of 40 days. Oct 2005, another two injection wells were treated by using the chosen technologic parameters of higher hydrochloric acid concentration and smaller volume of spacer with fluid A and B alternatively injected in small slugs in multiple cycles and were stimulated fairly effectively as to lowering injecting pressure and enhancing watertake in a not long time duration of 40 or 35 days.