Research On Development And Application Of New Drilling Fluid System Based On ST Oil

Horizontal well drilling technology is one of the key technologies for current oil and gas development. Increasingly complex drilling geological conditions proposed higher requirements on the performance of drilling fluid. Although conventional oil-based drilling fluid can meet the requirements of most drilling conditions of complicated formation. However, under the framework of environmental protection laws and regulations, conventional oil-based drilling fluid has many serious shortcomings:high aromatic content, high toxicity, pollution, etc. Such defects cannot reach the requirements. Taking Daqing Oilfield drilling company as an example, after the implementation of environmental law, the original diesel oil based drilling fluid has been totally forbidden. The need to develop a new oil-based drilling fluid system for horizontal drilling which meets the field requirements and achieves related environmental laws is extremely urgent.Aiming at the drawbacks of traditional base oil, a new ST oil is developed and evaluated in the laboratory systematically. The results show that the ST oil is better than diesel as base oil:low aromatic hydrocarbon content, and low toxicity. It will be the preferred base oil for environmental protection drilling fluid system.On this basis, we made indoor research for novel ST oil-based drilling fluid formula. By selection of emulsifier, filtration reducing agent, wetting agent and so on, we developed a novel ST oil-based drilling fluid system suitable for complex formation of Jilin Oilfield with good performance of temperature resistance, thermal stability, anti-pollution performance, inhibition performance, lubricating performance, and reservoir protection.We explored the possibility of the development of the application of novel ST oil-based drilling fluid horizontal development in Block Rang-53 of Jilin Oilfield as the research object. Firstly, the Fuzzy Comprehensive Evaluation Method is used to evaluated wellbore stability with the selected experimental data of of different layers of Block Rang-53.. The evaluation results show that in the condition of using water-based drilling fluid, it is easy for layers to collapse, prone to swelling, leading to wellbore instability phenomenon, greatly increased the difficulty of exploitation and construction cost. On the other hand, based on Block Rang-53 reservoir and formation fluid characteristics, the main damage mode of reservoir in the area is determined:water lock damage and water sensitive damage. The water locking damage mechanism, the main influence factors of the water locking damage is analyzed by the indoor experimental analysis, and quantitative evaluation of the extent of the damage are also determined.Finally, the invasion depth, cuttings recovery, sealing and expansion stress of novel ST oil-based drilling fluid all did field test in Jilin Oilfield. Research shows that compared to water-based drilling fluid, the novel ST oil-based drilling fluid can meet the requirements for reservoir protection and borehole stability requirements. Above all, the novel ST oil-based drilling fluid can be applied in drilling horizontal well in Jilin Oilfield.