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The relevance of the work. This paper provides a review of information on the structure and properties of oil reservoirs, on the conditions of concentration and filtration of oil in them. The use of horizontal wells, taking into account porosity and permeability properties of the reservoir, can significantly increase the contact area with an oil-saturated reservoir, ensure maximum development coverage and thereby reduce development time reducing the cost of oil production. Purpose of the work. The basic concepts of reservoir development and their application to horizontal wells in comparison with vertical wells are considered. Methods of research. A comparative analysis of the parameter of porosity and permeability properties of the production horizon, during the operation of its horizontal and vertical wells, is given. Results. The analysis of the skin zone influence on porosity and permeability properties of the reservoir. For a specific example, pressure losses were calculated for horizontal and vertical wells in order to conduct a comparative analysis of the wells under consideration. It is shown that for the same value of the positive skin factor, the pressure loss in the skin zone of a horizontal well is always less than its value in the vertical one. Horizontal wells can withstand a greater degree of damage than the vertical, without significant loss of flow rate. The analysis shows that a violation in the vicinity of the bottomhole zone, due to pore space bridging of the reservoir, leads to the formation of a zone with low permeability and additional pressure loss – the skin zone. Therefore, before making a decision on the impact on the bottomhole zone of a horizontal well, it is necessary to estimate the pressure drop in the skin zone and compare it with the total pressure drop between the reservoir and the bottom (the permeability of the skin zone with the reservoir permeability). Conclusions. For timely impact on the well bottomhole to improve the permeability of this zone and increase the productivity of the well, it is necessary to estimate the pressure drop in the skin zone.

This study presents an approximate analytical solution for predicting drawdown temperature transient behaviors of a fully penetrating vertical well in a two-zone radial composite reservoir system. The inner zone may represent a damaged (skin) zone, and the outer (non-skin) zone represents an infinitely extended reservoir. The analytical solution is obtained by solving the decoupled isothermal pressure diffusivity equation and temperature equation for the inner and outer zones with the Boltzmann transformation. The convection, transient adiabatic expansion and Joule–Thomson heating effects are all accounted for in the solution. The developed solution compares well with the results of a thermal numerical simulator. The analytical solution is used as a forward model for estimating the parameters of interest by nonlinear regression built on a gradient-based maximum likelihood estimation (MLE) method. A methodology, based on semilog analyses of pressure and temperature data as well as log–log diagnostic plots of pressure- and temperature-derivative data, is proposed to obtain good initial guesses of parameters, which derive the MLE objective function to have reliable optimized estimates. The statistical measures such as estimated standard deviation of noise in pressure and temperature data, confidence intervals for parameters and correlation coefficients between parameter pairs are used to evaluate the goodness of fit and reliability of the estimated parameters from history matching pressure and/or temperature data sets. The results show that the rock, fluid and thermal properties of the skin zone and non-skin zone can be reliably estimated by regressing on temperature transient data jointly with pressure transient data in the presence of noise.

The paper examines the possibility of hydraulic characterization of radial well laterals in a manner that does not require prior hydrodynamic analysis by simulating groundwater extraction conditions on a numerical model. The first step of the proposed approach is to assess the groundwater level regime formed in the capture zone when the well is operating, which is indicative of the functional condition of the laterals and the aquifer potential in terms of groundwater availability. Then the efficiency of the laterals is examined through the hydraulic function of the skin zone, depending on its filtration properties. An expression for groundwater flow from the aquifer to the laterals (commonly used to simulate laterals on a hydrodynamic model) is employed to define representative values of the conductance coefficient of the skin zone (as an indicator of colmation), and then applied to several wells at Belgrade Groundwater Source. The present research shows that a conductance coefficient of [Ks/ds]=1.0×10-4 s-1 can be considered as the threshold value in relation to which the effects of colmation of well laterals are exhibited, which is consistent with the results reported by researchers who studied the effect of skin zone conductance on the occurrence and nature of the so-called early drawdown at radial collector wells. In addition to gaining insight into the present condition of the laterals, the proposed approach can be used to study the progress of colmation at different points in time and to quantify the effectiveness of regeneration of laterals. [Projekat Ministarstva nauke Republike Srbije, br. OI176022, br. TR33039 i br. III43004]

Summary We analyze numerically the impact of key assumptions which are usually adopted to interpret borehole flowmeter test data. We base our work on a set of detailed numerical simulations of transient and pseudo-steady state convergent flow to a fully penetrating well that pumps at a constant total flow rate in a confined three-dimensional system formed by well demarcated facies. Our results allow identifying the effects of (i) the presence of a skin zone around the well, (ii) the contrast of hydraulic conductivities of the aquifer facies and the gravel pack, and (iii) the dynamics of the flow regime on the ability to characterize the local aquifer conductivities of a stratified system through the typical interpretation of downhole flowmeter tests. Vertical intervals along the wellbore, where reliable estimates of the aquifer conductivities can be obtained through classical formulations are identified in terms of a set of dimensionless parameters. These parameters involve the thickness of the facies constituting the stratified aquifer and the contrast of conductivities amongst different facies and between them and the skin zone.