溶洞堵漏用遇水增稠承托液的室内研究

处理大溶洞、大裂缝引起的失返性漏失,目前主要采用水泥浆进行堵漏。施工中,在注入水泥浆之前,需注入起承托作用的高黏度承托液,保证水泥浆停留洞口,从而达到堵漏目的。目前常用的承托液主要以高黏度稠浆为主,极易被地层水冲稀,无法起到承托目的。通过室内合成高分子聚合物YSZC-1,并将YSZC-1与油基液体复配,形成一种遇水增稠型油基承托液,该承托液黏度可调,能满足现场施工要求。遇水增稠的特性从根本上避免了承托液被冲稀导致溶洞堵漏失败的可能。该承托液与清水、水基钻井液混合后,表观黏度呈指数级上升,承托液与水基钻井液按照体积比1:1混合时,混合后承托液黏度最大,体积比上升至1:9时承托液表观黏度仍然达到133 mPa·s,具有很强的抗稀释性,在150℃,老化16 h,表观黏度无明显下降。该承托液抗盐能力达到饱和,抗Ca2+能力在5%左右,具有很好的抗盐性,与水泥浆有较好的相容性,不会造成水泥浆“闪凝”影响施工安全,能满足溶洞堵漏对承托液的各项要求,提高溶洞堵漏成功率。 

Study on Water Thickening Supporting Fluid for Controlling Mud Loss into Caves

When lost circulation is encountered during drilling into big caves or macro fractures, squeezing cement slurry is the commonly used method to control the mud losses. When squeezing cement slurry, a highly thickened supporting fluid shall be spotted into the loss zones to support the cement slurry, making sure that the cement slurry stays in place and sets at the mouth of the cave, thereby stops mud losses. The supporting fluids commonly used presently are high viscosity bentonite slurries which are easy to be diluted by water, and therefore cannot support the cement slurries. To formulate a suitable supporting fluid, a high molecular weight polymer, YSZC-1, was synthesized. An oil base supporting fluid, viscosified when in contact with water, was formulated by mixing YSZC-1 with oil. The viscosity of this supporting fluid is adjustable to satisfy the special needs of field operation. Since this supporting fluid instantly becomes thickened as soon as it is in contact with water, it cannot be diluted with water, and the failure in controlling mud losses into caves can thus be avoided. When in contact with water or water base drilling fluid, the apparent viscosity of this supporting fluid increases exponentially, and to a maximum when the volume ratio of the supporting fluid and water base mud is 1：1. An apparent viscosity of 133 mPa·s was obtained by mixing one part (volume) of supporting fluid with 9 part of water base drilling fluid, rendering the supporting fluid strong resistance to water dilution. When aging for 16 h at 150℃, the apparent viscosity did not decrease apparently. This supporting fluid is resistant to salt contamination to saturation, and to calcium contamination to about 5%. It is compatible with cement slurry, and will not cause the cement slurry to "flash set". This supporting fluid satisfies the needs for controlling mud losses into caves, and maximizes the possibility of successful mud loss control in caved formations.