Research On Bakken Tight Oil Reservoir Characteristics And Multi Fracturing Horizontal Well Development Techeneque

Tight oil and gas belonged to the unconventional resource which attracts a lot of attention by the international oil and gas companies in recent years. How to economically exploit tight oil and gas is a new challenge for the world.The dissertation selected the Middle Bakken Formation of Williston basin in Saskatchewan as a research object to evaluate the formation characteristics and the multi fracturing horizontal well technique. Conclusions and results were made as follows:(1) The middle Bakken formation could be divided into two lithofacies group as FG1and FG2. The two lithofacies group represented different depositional environments. FG1could be divided into two lithofacies:BF1, massive silty sandstone; BF2, ripple laminated sandy siltstone. FG2could be divided into three lithofacies:BF3, thinly bedded sandstone; BF4, interbedded sandy siltstone; BF5, bioturbated siltstone.(2) The different lithofacies have different mineral components. Petrographic research and mineral analysis found that the dolomite and calcite was the main cements of the Bakken formation. Secondary porosity is the main porosity type. In general, the lower content of the total cements is, the bigger the secondary porosity would be. The rock structures of the five lithofacies were similar and belonged to mechanical compaction. The diagenesis of different period changed the original content of the cements and the original porosity.Combined with lithofacies analysis and petrographic research, laboratory experiments were made to study the porosity and permeability characteristics of the Bakken formation. And the Bakken formation was divided into smaller formations as A, B, C, D, E. With the results made above, A and E formation were defined as non-reservoir, B formation was defined as marginal reservoir, C formation was defined as the main reservoir, D formation was defined as potential reservoir.(3) The utilization of multi fracturing horizontal well has proved to be an effective manners to economically develop the middle Bakken formation. From the production curve analysis, the linear flow was the main flow type of the tight oil reservoir. The reservoir characteristic parameters, horizontal well parameters and OOIP could be estimated from the slope and the intercept of the special production curves. Production prediction was also made to the Bakken tight oil. In the end, a multi fracturing horizontal model considering the dual porosity was established to illustrate some perceptual knowledge for the tight oil production. The main result was that because of the extremely low permeability of the matrix, the main flow regime of the tight reservoir was limited in the reservoir which was controlled by the hydraulic fractures. The main effect of the hydraulic fracture was to connect the natural fractures with the horizontal wellbores that is to rejuvenate the original natural fractures. This idea was quite different with normal explanation of the low permeability reservoir which believed that the well performance could be largely enhanced by increased the conductivity of the hydraulic fractures and only3-5fracures could bring a good effect.