Study On Anti-Collapse Drilling Fluid In Shale Of Yuguo In Tuha Oilfield

In recent years, Western Drilling Company often encountered that the borehole is proneto collapse, and other complex issues happen all the time in Tuha oilfield. During the drillingprocess, these phenomenons are commonly meet, such as trip blocking, sticking, drilling pipebreaking, even without well completion, which causing great economic losses. In the light ofshale wellbore instability in Tuha oilfield, this paper has researched the mechanism of claylayer borehole instability by co-utilizing all the methods of X-ray diffraction, SEM, hydrateexpansion and dispersion and specific water wettability, et al. It proposed the effectively plug,reasonable density to support, lay stress on inhibiting surface hydration multiple elementscooperation anti-collapse technical strategy, and further more, probed into the mechanism of it.At last, a high effective cooperation anti-collapse drillingfluid formula has been developed,which achieved good feedbacks in field applications.Experimental studies have shown that the shale in Tuha oilfield region has the followingdistinguishing features such as mineral cemented, bedding, micro-fissures, hydration andstrong dispersion, low thermal expansion and low CEC and other characteristics, but itssurface hydration ability and local hydration cause borehole instability easily.Based on the basic principles of the "synergistic diversifications" for anti-collapse ofdrilling fluid, Many treatment agents are selected, such as a strong inhibition of polyamineagent SDJA, agent CMC-HV. Preferred in molecular polymer fluid loss additive PJA-2, resinfiltration reducer loss agent SHR-1, lignite class Filtrate Reducer CXB-1, the lubricantJXFQ-2are optimized. And high performance anti-collapse drilling fluid formula isconstructed according to the multiple elements cooperation anti-collapse theory. Theanti-collapse drilling fluid formula posses good performances，such as sealing，inhibition,rheology behavior, lubricity, heat resistance, et al. The properties are better than the presenton-site drilling fluid formula. The anti-collapse drilling fluid with good resistance to weightup, salt, poor soil possesses good performances,such as sealing, inhibition and rheology behavior.According to results on-site in well Guo802of Tuha oilfield, it has manyperformances,such as good lubricity, good stability in high temperature, and it is easy tomaintain. This shows that the newly develop ed anti-collapse drilling fluid has stronganti-collapse capability, and meets the construction requirments of shale in Tuha oilfiled.