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The upper layer of Oil field A is developed by horizontal linear well pattern with long well segment. After completion, there is relatively serious formation damage, and the tested epidermal factor is up to 6.21 on average. Due to the length of horizontal well section and the serious vertical heterogeneity of formation, some strata were over-acidized in the early stage, so it was very difficult to distribute acid evenly. For this reason, the low contribution layer of horizontal section was determined by using amino carboxylic acid system and coiled tubing hydrojet acidification process, combined with reservoir characteristics, and the spindle-type acid distribution method was adopted to optimize nozzle combination parameters to predict construction displacement and ground construction pressure. The laboratory experiment was carried out to compare with the conventional acid system for core displacement experiment. The acid could form acid-etch wormhole, effectively extend the acid-action distance, and achieve the purpose of slow and deep penetration.

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Aiming at the problem of shortage of clean water resources and mixing fracturing fluid in winter in Erlian oilfield, the technology of producing water to prepare fracturing fluid was studied. Horizontal comparison of water samples from four combined oil and gas treatment stations shows that oil, surfactant and bacteria are the main factors that affect the indigestion of hydroxypropyl guar gum in oilfield produced water. Through the indoor research developed a new type of multi-functional cosolvent and explored the oilfield produced water confecting fracturing fluid formulation system: 0.3-0.5% hydroxypropyl guar gum +X% multifunctional cosolvent + 0.2% flow-back agent + 0.4-0.6% crosslinking agent. This technology simplifies the mixing process and reduces the amount of additives. The liquid still has a high viscosity after being placed for more than 3 to 4 days in summer. In winter, using the produced water for mixing can reduce the influence of environmental temperature and ensure the smooth construction. After field application in well h5-19, the effect is outstanding, which provides important technical support for follow-up fracturing construction in Erlian oilfield.

Over-displacement technology often occurs in the fracturing process of horizontal gas wells. The effect of horizontal shale gas wells productivity with different fracture morphology considering over-displacement were analyzed by numerical simulation. The results show that the over-displacement productivity is only 12.3%-15.0% of the equilibrium displacement productivity considering the complete fracture closure, and the fracture morphology has no effect on the productivity. Therefore, the amount of over-displacement hydrofrac fluid should be minimized in horizontal gas well, the fracturing fluid can rapidly gel-break and flowback after fracturing, proppant can flow back or settle at the fracture seam, and complex fractures can be formed near the wellbore as far as possible, so that it can reduce the impact of over-displacement on productivity. This study can provide a theoretical basis for fracturing design and productivity prediction of horizontal gas wells.