Oil & Gas Research
Open Access

A study of pressure transients in naturally fractured reservoirs

In naturally fractured reservoirs, pressure transient experiments frequently show non-uniform responses. In order to appropriately characterise reservoir parameters, many methodologies can be utilised to examine pressure behaviour in dual porosity reservoirs. Traditional semi-log analysis, type curve matching (using commercial software), and Tiab's Direct Synthesis (TDS) techniques were used to analyse pressure transient testing in naturally fractured reservoirs in this paper. In the event of a naturally fractured formation with a vertical hydraulic fracture, the TDS approach was also used. Under pseudo steady state matrix flow, these techniques were applied to a single layer naturally cracked reservoir. Various reservoir characteristics, such as permeability and skin, can be derived by observing the distinct characteristics of the different flow regimes that appear on the pressure and pressure derivative curves in skin factor, and fracture properties. A comparison of the findings of semi-log analysis, software matching, and the TDS method for naturally fractured reservoirs is presented. In the case of wellbore storage, the early time flow regime can be masked, resulting in a semi-log analysis that is incomplete. Furthermore, because all of the flow regimes must be observed, type curve matching frequently results in a non-uniqueness solution. The direct synthesis approach, on the other hand, used an analytical equation to calculate reservoir and well parameters without having to match type curves. The pressure behaviour of wells crossed by a uniform flux and infinite conductivity fracture is investigated using the TDS technique for naturally fractured reservoirs with a vertical fracture. The fracture half-length, as well as other reservoir properties, was calculated using the different flow regimes on the pressure derivative curve. When compared to semi-log analysis and type curve matching, the findings of several scenarios revealed that the TDS technique has significant advantages. Even if particular flow regimes are not observed, it can be employed. When compared to the available core data and software matching results, direct synthesis results are accurate.

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