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Hydraulic Fracturing, Proppant, Acid FracturingAbstract. Increase in the price of oil and gas during recent years have motivated oil and gas companies to focus on the methods that lead to increasing in the oil and gas production. Oil well stimulation as one of these methods includes a variety of operations that performed to improve productivity of the well. The main objective of a stimulation treatment is to increase the rate at which the formation delivers hydrocarbons naturally. Today’s well stimulation method is converted to the appropriate method in the oil and gas industry to maintain or increase of well productivity. Injection of acid to partially dissolve the rock, and hydraulic fracturing to split the rock and prop it open with proppant are two common techniques for stimulating of the wells. Deciding about selection of the best method for stimulation of the wells is related to the comprehensive evaluation of capabilities of each technique and conditions which are governed on specific job intended. In this article, we are trying to present a description about well stimulation method, methods that are employed to execute well stimulation, and application of these different techniques for stimulating of wells.

The problem of selecting a target formation(s) in a reservoir among a vast number of zones/sublayers within huge number of hydrocarbon producing wells for hydraulic fracturing (HF) by using interval type-2 fuzzy logic system (IT2-FLS) to maximize their net present value is studied in this paper. Classical fuzzy system which is called type-1 fuzzy logic system is not capable of accurately capturing the linguistic and numerical uncertainties in the terms used and the inconsistency of the expert's decision-making. IT2-FLS is very useful in circumstances where it is difficult to determine an exact membership function for a fuzzy set; hence it is very effective for dealing with uncertainties. In highlighting this need, the question has been answered why IT2-FLS should be used in this study. The procedure of applying this study in the area of HF candidate-well selection is illustrated through a case study in an oil reservoir.