Evaluation method of single well nitrogen injection effect in carbonate fracture-cavity reservoir

Abstract

The invention discloses a method for evaluating the effect of nitrogen injection in a single well of a carbonate fracture-cavity reservoir. Calculate the gas storage rate based on the gas production rate, the average content of nitrogen in the gas components in the well-opening production period after nitrogen injection, and the cumulative nitrogen injection volume in the cycle; calculate the gas storage rate based on the cumulative oil production in the well-opening production cycle after nitrogen injection and the cumulative nitrogen injection volume in the cycle Obtain the underground gas-oil exchange rate; according to the critical oil increase value of nitrogen injection in a single well, the gas storage rate, and the underground gas-oil exchange rate, combined with the recoverable reserves of remaining oil in a single well, obtain carbonate fractures Evaluation information of single well nitrogen injection effect in cave-type reservoirs. The invention provides a basis for single well nitrogen injection effect evaluation and process optimization, makes the oil well nitrogen injection effect evaluation more targeted, and makes the nitrogen injection effect evaluation standardization in carbonate fracture-cavity reservoirs.

Description

technical field [0001] The invention relates to the technical field of petroleum development, in particular to a method for evaluating the nitrogen injection effect of a single well in a carbonate fracture-cavity reservoir. Background technique [0002] The fractured-cavity carbonate reservoir in Tahe Oilfield is currently the largest carbonate reservoir in China. By the end of 2014, the accumulated proven oil geological reserves of this reservoir were 125847×10 4 t, used crude oil geological reserves 82854×10 4 t, recoverable reserves 11988×10 4 t. Tahe Oilfield carbonate fractured-vuggy reservoir is extremely special, with deep burial and various storage spaces. The reservoir is highly heterogeneous, the oil-water relationship is extremely complex, and the reservoir has no unified oil-water interface. By the end of 2014, the recovery rate was only 14.5%. [0003] In 2012, Tahe Oilfield carried out a pilot field test of nitrogen injection in carbonate fracture-cavity re...

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Problems solved by technology

[0004] 1) Carbonate fracture-cavity reservoirs have strong heterogeneity, reservoir scale changes, oil well development is complicated, and there are no rules to follow. After gas injection, the effect evaluation method is single, relying only on oil increase and water cut It is no longer possible to correctly judge whether the gas injection is effective;

[0005] 2) After nitrogen injection, it has played a role in the formation, but the effect is only judged based on "increasing oil and reducing water", which cannot objectively and truly evaluate the effect of nitrogen injection on the formation, and cannot provide guidance for the optimization of nitrogen injection parameters in oil wells

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