大情字井地区储层损害机理及保护储层技术

大情字井地区储层损害问题是钻井完井液固相侵入微裂缝或漏失引起的固相堵塞损害，钻井完井液的滤液侵入储层引起的水敏、水锁和碱敏损害，注水速度过快引起的速敏性损害，以及含高价阳离子的完井液滤液侵入储层引起的无机垢损害。通过分析储层损害因素，制定了一套适合该地区钻井完井液技术。即：①增强钻井完井液滤液的抑制性，降低滤液表面张力；②降低钻井液完井液的滤失量；③配制完井液时，注意其离子含量和矿化度，必须接近地层水的矿化度和离子组成；④在钻井完井液中加入适当粒度的固相粒子，以便形成致密滤饼，降低钻井完井液体系的滤失量，同时对低渗透储层的微裂缝起到一定的封堵作用；⑤为了减轻碱敏损害的程度，钻井完井液的pH最好控制在10左右。该套钻井完井液技术在现场实验中取得了良好效果。

Formation damage mechanisms and protection technologies in Daqingzijing area

The types of formation damages in Daqingzijing area are described, i. e. , solids blocking damage because of the invasion of drill-in fluid solids into micro fractures or lost circulation; water blocking, water sensitivity and alkali sensitivity damages because of the invasion of drill-in fluid filtrate into formation; velocity damage because of the excessive water injection speed; inorganic scale damage of the invasion of high valency cationic drill-in fluid filtrate into formation. By evaluating the causes of formation damage, a set of drill-in fluid technologies is presented, consisting of the following aspects: 1. strengthening the inhibition of drill-in fluid filtrate and reducing its surface tension; 2. reducing the filtration of drilling fluid and completion fluid; 3. when batching the completion fluid, attention should be paid on its ions content and salinity, and the ions composition and salinity should be similar with that of the formation fluid; 4. adding solid fines of suitable granularity into the drill-in fluid, so as to form tense filtrate cake and reduce the filtration of the system, meanwhile plug the micro fractures in the low permeability formation; 5. controlling the pH value of the drill-in fluid at about 10, to minimize the degree of alkali sensitivity damage. This set of drilling fluid technologies has been field tested with good results obtained.