In the process of oil drilling, drilling fluid plays a dual role in preventing wellbore leakage and protecting oil and gas reservoirs. But these two roles sometimes have sharp contradictions. When encountering oil and gas enriched formations during drilling, the characteristics of the formations are often unstable, and complex situations such as leakage and collapse are prone to occur. At this time, the wall protection and leak prevention function of the drilling fluid is particularly important. In order for ordinary drilling fluid to have a good wall protection and leak prevention effect, it is necessary to increase its solid content and viscosity, but this will also bring about the phenomenon of polluting the oil and gas reservoir. How to effectively manage the problem of wellbore leakage and collapse while also protecting oil and gas reservoirs has become a major challenge in the field of oil drilling in China.
According to Guo Baoyu, Chief Scientist of Shengli Oilfield Drilling Engineering Technology Company, the newly identified new drilling fluid system can form a thin and tough diaphragm on the wellbore wall. This diaphragm has extremely low permeability and forms a protective wall layer with almost zero permeability near the wellbore wall, achieving a good effect of maintaining wellbore stability.
As time goes by, when it is necessary to open the oil and gas reservoir, biological enzymes begin to exert their biodegradation effect, gradually breaking the originally tough and dense protective film. At this time, active biological enzymes slowly enter the reservoir, grow and reproduce under the oil film on the rock surface, causing crude oil to peel off from the rock surface and be driven out; At the same time, it can also degrade crude oil, enhance its flow capacity, and fundamentally achieve the goal of improving crude oil recovery.
It is reported that field tests conducted on 34 wells in Qudi Oilfield, Huaibei Oilfield, and Jilin Oilfield have shown that the average crude oil recovery rate has increased by more than 25%, and the permeability of the formation has been restored to over 90%. This system has broad development prospects in liberating oil and gas reservoirs and protecting them.