A Study On Interval Speed Technology From Middle To Bottom Part Of The Tight Sandstone Reservoir In Baka

At Baka sub mountain region of Tuha Oil Field, the high steep structure outstanding shows many drilling difficulties in the drilling process, such as the uncontrollable well bore quality, great depth, long cycle length, slow penetration rate, low aging pure drill and coal formation drilling safety problems.On account of the characteristics of the Baka block’s tight sandstone reservoir, it is necessary to have a study on interval speed technology from middle to bottom part. But the contradiction between these and to develop Baka sub mountain region’s structure reservoirs efficiently is prominent. Therefore, on basis of analyzing the current drilling situation in Baka block of Tuha Oil Field and the actual existence of all kinds of difficulties of its high steep structure, the paper carried out many researches accordingly from various aspects in order to adapt to the needs of the drilling development and solve the problem of the slow penetration rate. The formation deflecting law and anti-deflection drilling, mechanism of coal beds and safety drilling technology, rock mechanics characteristic and well wall stability were fully studied. This paper optimized research on well wall’s collapse mechanism, inclining-prevention drilling assembly and wellbore structure.Through the analysis of complex geological conditions to Khartoum compacted sandstone gas reservoir, the paper gives the formation characteristics:poor drillabilityr, slow mechanical drilling speed. large stratum dip angle, and the well be easy to inclined, and the well body quality difficult to control, the contradiction stick out between inclined and playing fast.It including that coal seam is much, sidewall stability is poor, collapse accident led to more complexity. Through the regularity of distribution to the Baka block pore pressure rule of strata, the paper studies obtain vertical and horizontal change of equivalent density values of he structure at each layer of a formation pore pressure. With profound determination of the rock mechanics parameters and ground stress method, determine the stress profile. Through the research of coal seam instability mechanism, stability analysis and establish model, and it obtains that the simulation results and make corresponding countermeasures, to form a set of effective coal safety drilling technology, and determine the reasonable safety drilling fluid density window. Combining with the above results, conduct the research of optimization design to the well body structure. Through the research. layer of stratum made, develop the block the inclined playing fast technology research.Through a lot of foundation technology research work and field test, a series of high-speed drilling technology of high steep structure’s lower layer in Baka sub mountain was formed. It improved the success of the block exploration and development speed and provided a strong technical support while realizing development principle of "safe, efficient, superior quality and economic".After subject study and applying in oilfield, the penetration rate increased by more than15%and complex accidents aging could drop by50percent. The paper has got the following innovation points. First, by the study of well bore stability and sloughing mechanism of coal beds, a set of effective safety drilling technology which caters to lower part of Baka is set up. Secondly, by the study of the formation deflecting law, anti-deflection drilling technology which is fit for lower layer of Baka is also established.