无自由水压井液研制与应用

Development and Uses of Well Control Fluid without Free Water

已进入开发中后期的吐哈油田大部分区块井底压力低,为此开发了无自由水压井液。通过固化剂(高分子吸水材料)等组分筛选,得到了压井液优选配方:清水+1.0%KEG-CA-3(丙烯酰胺接枝纤维素共聚物)+0.3%固化引发剂+0.5%胶体保护剂+1.0%KCl+0.4%NaHCO3;其表观黏度为50mPa·s,API和HPHT滤失量分别为19.6、29.0mL,在砂床上无滤失,进入砂床深度14.3cm。该压井液在80℃、30天老化过程中及在100℃热滚16小时后,流变性变化小,滤失量有所增大;储层岩心粉在该压井液滤液中浸泡16小时,膨胀高度仅为0.63mm(在清水中为3.04mm);在储层岩心实验中,注入并返排后油相渗透率>82%,切去污染端2cm后渗透率恢复率>96%,除去滤饼后在≤12MPa压差下不渗透。该压井液已成功应用27井次。与使用常规压井液的一口井相比,使用该压井液施工的一口井,作业后生产恢复稳定所需时间很短,产出的原油含水率低。

A well control fluid（WCF） without free water was prepared for use in Turpan-Hami oil fields at middle-late stages of development,where the well bottom pressure at most reservoirs was low. Through sieving experiment of water retaining and other additives,an optimal formulation of WCF was obtained： 1.0% KEG-CA-3 （cellulose-g-polyacrylamide, water retaining additive） ＋ 0. 3% initiator ＋0. 5% gel protector ＋ 1. 0% KC1 ＋ 0. 4% NaHCO3 ＋ fresh water and it was characterized by following parameters： apparent viscosity 50 mPa.s; API and HTHP filtrate loss 19. 6 and 29.0 mL; no filtration in sand bed test;entrance depth in sand bed 14. 3 cm. Its rheologic characteristics changed slightly and its filtrate losses increased to some extent in the course of thermal ageing at 80℃ in 30 days and after rolling at 100℃ over 16 hrs. The height of swelled reservoir core powder in the WCF filtrate was 0. 63 mm only in contrast to 3.04 mm in fresh water. The percentage permeability recovery of the reservoir cores polluted by this WCF was of 〉 82% after backflow of the WCF and 〉 96% after 2 cm long polluted end being be cut;zero permeability was measured under pressure ≤ 12 MPa for the polluted reservoir cores with the filter cake of WCF removed. This WCF without free water was used successfully 27 well-times. The time needed for a well to recovery its steady productivity was much more short and the watercut of produced crude was lower after finishing workover job with WCF without free water comparing to that in job with conventional WCF used.