Characteristics of non-Darcy flow in low-permeability reservoirs

Abstract

Well testing is recognized as an effective means of accurately obtaining the formation parameters of low-permeability reservoirs and effectively analyzing the deliverability. Well test models must comply with the particular characteristics of flow in low-permeability reservoirs in order to obtain reasonable well test interpretation. At present, non-Darcy fl ow in low-permeability reservoirs is attracting much attention. In this study, displacement tests were conducted on typical cores taken from low-permeability reservoirs. Two dimensionless variables were introduced to analyze the collected experimental data. The results of the dimensionless analysis show whether non-Darcy fl ow happens or not depends on the properties of fl uid and porous media and the pressure differential. The combination of the above three parameters was named as dimensionless criteria coeffi cient (DCC). When the value of the DCC was lower than a critical Reynolds number (CRN), the fl ow could not be well described by Darcy's law (so-called non-Darcy fl ow), when the DCC was higher than CRN, the fl ow obeyed Darcy's law. Finally, this paper establishes a transient mathematical model considering Darcy flow and nonDarcy fl ow in low-permeability reservoirs, and proposes a methodology to solve the model. The solution technique, which is based on the Boltzmann transformation, is well suited for solving the flow model of low-permeability reservoirs. Based on the typical curves analysis, it was found that the pressure and its derivative curves were determined by such parameters as non-Darcy flow index and the flow characteristics. The results can be used for well test analysis of low-permeability reservoirs.

Exact analytical solutions of moving boundary problems of one-dimensional flow in semi-infinite long porous media with threshold pressure gradient

“…The research on the flow in porous media with threshold pressure gradient has a wide variety of practical applications [1][2][3][4][5][6][7][8][9][10][11][12] in the development of low-permeability reservoirs, polymer injections in enhanced oil recovery, the non-Newtonian Bingham fluid flow in heavy oil reservoir, consolidation of clayey soils, proppant suspension during the hydraulic fracturing operations and so on. Various attempts to model the flow in porous media with threshold pressure gradient can be found in the literature.…”

Waterflooding Huff-n-puff in Tight Oil Cores Using Online Nuclear Magnetic Resonance

“…Because of the very low permeability and non-Darcy flow in tight oil reservoirs [5][6][7], a starting pressure gradient exists during waterflooding development, which leads to difficulties during injection, a rapid production decline [8][9][10], and insufficient formation energy challenges [11]. The development of tight oil reservoirs has mainly focused on the combination of horizontal wells and volume fracturing [12][13][14].…”

Dynamic Behavior of the Polished Rod for the Coalbed Methane Pumping Installations

“…Therefore, these simplified modeling procedures, if applied to the producing CBM wells, could not help one to identify the specific phenomena that occur during the production and do not give the desired results to predict dynamic behavior of the polished rod. The reason is mainly that there exists the differences between conventional gas formations and CBM well conditions [14,15], including shallow well depth, low water production, high dynamic fluid level, short stroke and pumping speed dropping down rapidly. Another aspect to consider is that the dynamic behavior of polished rod for CBM pumping installations has not been further developed and the available procedures do not provide the desired accuracy of the system designing and its pertinent analysis.…”