The Research On Reservoir Fracture Method And Applications Of Low Permeability Reservoirs Of Beach Bar Sand In Dongying Depression

Aiming at researching for the beach bar sandstones reservoirs distribute in the fourth member of Shahejie formation of Dongying sag, from such aspects as the regional structure, effective reservoir, sedimentary system and formation pressure sand as well, the formation, distribution, characteristic and types of this reservoir were all discussed in this paper, so that the research results will be helpful for the reservoir treatment approaches in geologic and reservoir aspects.It indicated that it widely distributed in the planar direction. It tends to be such features as followings, more beach sandstones and less bar sandstones, plentiful inter-bedded layers in the horizontal direction, longer hydrocarbon-bearing, deep buried depth, and also lower abundance and even lie closely to the generation center of source rocks for the reason of smaller effective reservoir thickness and lower permeability. What’s more, the filtering of fracturing fluids is heavy and striking rules of fissures are complex owing to the possibility of fractures opening during the hydraulic fractured treatment because of abundant micro-fractures and natural fractures in the reservoirs. Furthermore, it is very important for the prediction and controlling for fractures height and striking of hydraulic fractures which are caused by the hydraulic operation owing to thinner effective thickness and interbedded layer occurred alternatively. The study on software development for fractures prediction and filtering treatment are conducted in this paper, on the basis of features analysis and classifications for beach and bar sandstones reservoirs in the fourth member of Dongying formation, and the corresponding reservoirs modification approaches, such as the reservoirs protection, optimizing for fractures designing parameters and matched techniques, choosing rules for the fractured operational technique on classified layers, system development for acidified and sand-adding into fluids, were considered as well.The special fractured fluids, the VES was optimized to fractured modification for the consideration of reservoir protection because its damage to reservoir and the fracture deflecting is far more less than the normal aqueous fracturing fluids, and with no residues or filter cake. However, when not allowing the VES fluid, aqueous fracturing fluid should be used with adding the anti-swelling agents or the layer can be processed with the Waterproof agents preferentially to reduce the damage on the reservoir. Also before the fracturing, the waterproof agents can be used to increase the flowback ratios of the fracture fluids.Based on the analyzing on reservoirs property, fluids types and data from earlier hydrocarbon test of the beach bar sandstones, study on mechanical parameters and sensitive experiments were conducted firstly, and then the influence factors on the reservoirs were all considered by using of lots of experiment, research and dynamic simulation, so that the matched fractured techniques corresponding to different permeability zones were worked out.Based on the current fracturing process adaptability of the beach bar reservoirs, five types of the fracturing technologies have been assessed. Then, the separated layer fracturing integrated tools were developed with one hundred meter distance and tested successfully. According to the reservoir conditions, the limited fracturing technology and pitching temporary plugging fracturing technology, reducing leak off technology and fracture height technology, and flowback technology can be chosen.In addition, cross-linked acid viscosifying agents and cross-linking agents have been developed for the consideration of requirements on acidifying and sand-adding for the beach development with higher dolomites-bearing. The polymer type name is PAM-Ⅱ. The cross-linking agents used the organic or inorganic additives. According to the polymer viscosifying agents and cross-linking agents used, the fluids can be changed into network jelly systems which are suitable in the beach bar layers. Based on it, the new type of the cross linked acids was developed which was characterized by the higher viscosity, lower leaking and friction, easily pumping, slow acid rock reaction, higher fracturing ratios, flow back, better rheological property and carrying sand. This type of system reaches to the deeper acid fluid across, increasing the acid fracturing ability and extending the well production after fracturing and takes effect on the acid fracture and prop fracture to improve the flow conductivity of the artificial fractures.Finally, it indicated the better application effects when the matched treatment method was used in the practical operation.