For high permeability sandstone, the invasion of particles and the filtrate of drilling fluids is proven as one of the key factors accounting for reservoir damage. However, it is difficult to determine the invasion depth of particles and the filtrate of drilling fluids by using mathematical model. The novel invasion models of particles and the filtrate of drilling fluids are built up in dynamic condition by the mass conservation equation and radial friction loss equation, especially for the models taking into account the external and internal mud cake at the same time. Parameters of models are determined by experiments of API filter loss and dynamic filtrate loss. The simulating results indicate that the invasion depth of particles is deeper when the core permeability is higher. The invasion depth of the filtrate is influenced seriously by the different pressure, the viscosity of filtrate, the permeability and thickness of external and internal mud cake. Howerver, permeability and fluid viscosity of reservoir have little influence on the filtrate invasion depth.The zwitterionic polymer drilling fluids are optimized. In an addition, ideal packing approach is applied to the drilling fluids. The instrument of dynamic fluid loss test is used to evaluate return permeability. The test results indicate that the ideal packing approach can reduce the dynamic filtrate loss. It also can improve the return permeability and reduce breakthrough pressure. The predicted results of this model indicate that the invasion depth of particles and filter is deeper without bridging agents. Ideal packing approach can reduce formation damage.
Tight oil can be commercially recovered by horizontal well multistage fracturing. With the development of multistage fracturing tools, extended reach horizontal well could be a way to enhance unconventional tight oil economical efficiency. On the base of the study on Cardium formation, fracturing fluids were analyzed and slick water fracturing fluid was optimized. Frac port multistage fracturing string was studied and applied in pilot tests. Three extended reach horizontal wells with average 40 stages and 2954m horizontal length pilot tests were applied and studied. Comparison of well costs and production between extended reach horizontal wells and offset short horizontal wells were studied, extended horizontal reach wells get much more profits after six months producing when oil price above 101 CAD/bbl, and save 50% well construction costs and producing management costs.
The best is to read these instructions and follow the outline of this text. To improve the injection steam enthalpy is the key technology in ultra-heavy oil thermal development. The wellbore heat insulation technology is needed to keep the process of steam injection hot enthalpy, to reduce heat loss utmost, to prevent the damage of the casings and cement mantle in high-temperature steam. The conventional cased-hole completions require the borehole thermally insulating insulation technology in thermal recovery, and generally adopt insulated tubing steam injection, ordinary tubing transfer pumping, which will cause frequent operations and enlarge the accidental risks caused by a number of down hole tools which are tripped in wellbore. Insulation casing well completion technology can effectively solve the wellbore insulation problems, and improve the casing and cement mantle security, increase the production rate. The field applications in Henan Oilfield have obtained excellent results; two wells were operated with completion technique by heat insulated casings. Compared with the same types of wells in the pilot test ultra-heavy oil block, the production is about twice as much as those of other wells, and the economic effect is obvious.
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