Search

Abstract The study focuses on building a 3D-dimensional model for using well log data of 3 wells to enable a better understanding of the reservoir characteristics and evaluation of the hydrocarbon potential in the field of Ronier in the Bongor Basin, Chad. These data are used to build a Lithofacies model, property model, the permeability model and the saturation model which are the parameters that describe the reservoir. Indeed, the accuracy to quantify the geological reserve of Ronier 4 reservoir block depends on the estimation of these values. The result of geological modeling and upscaling of the Ronier 4 block of Ronier oilfield is presented systematically. In this work, a Sequential Gaussian Simulation (SGS) algorithm under the phase control based on the collocated co-Kriging is adopted and the models of porosity, permeability and saturation are established. Lithofacies model has sand (0) content of 66.69% mostly the first layer, while the code (2) shale content 12.15% mostly concentrated in the center, north and south. Finally, the code (3) sand content is 21.16%. The NTG distribution is highly concentrated in the north, center and south (1) and 0.7 on average, while the lowest range is 0.1. The study shows a good permeability range between 460 to 1200 and 500 mD on average. The porosity distribution mainly distributed between 17 to 27 and 19% on average. These indicate that it has good reservoir properties. The 3D developed geological model provides the basis for calculating the Oil Initially in Place (OIIP) volumes of hydrocarbons.

In this paper, the mathematical model of production performance analysis for horizontal wells in composite coal bed methane reservoir is introduced. In this model, two regions with different formation parameters are distinguished, and multiple mechanisms are considered including desorption, diffusion, and viscous flow. Then the solution of horizontal well performance analysis model is obtained by using point source function method, Laplace transform, and Stehfest algorithm comprehensively. The solution of the proposed model is verified with previous work thoroughly. The pressure transient analysis for horizontal well when producing at a constant rate is obtained and discussed. At last, different flow regimes are divided based on pressure transient analysis curves. They are early wellbore storage period, skin factor period, first radial flow regime, transition regime, second radial flow regime, transfer regime, and late pseudo-radial flow regime. The effects of related parameters such as storativity ratio, transfer coefficient, adsorption coefficient, ratio of vertical permeability to horizontal permeability, skin factor, horizontal well position in vertical direction, and inner region radius are analyzed as well according to pressure transient analysis and rate transient analysis curves. The presented work in this paper can give a better understanding of coal bed methane production performance in composite reservoir.

Since the classical seepage theory has limitations in characterizing the heterogeneity of fractured-vuggy tight reservoirs, well test interpretation results are not consistent with actual production by far. Based on the nonlinear percolation theory, a new nonlinear seepage equation considering the boundary layer and yield stress was derived to describe the seepage characteristics of dense matrix blocks and the stress sensitivity and fractal features of fracture systems were characterized by applying the fractal theory. Thus, the nonlinear model of a horizontal well in a fractured-vuggy tight fractal reservoir was established naturally. Then the finite element method was applied to solve the bottom hole pressure based on the processing of internal boundary conditions. After solving the model, the seepage characteristics of different models were summarized by analyzing the bottom hole pressure dynamic curves and the sensitivity analysis of multiple parameters such the nonlinear parameter and fractal index were conducted. Finally, the practicality of the model was proved through a field application. The results show that the pressure dynamic curves can be divided into nine flow stages and the increase of the nonlinear parameter will cause the intensity of the cross flow from matrix blocks to the fracture system to decrease. The fractal index is irrelevant to the intensity of the cross flow while it decides the upwarping degree of the curve at the middle and late flow stages. On the basis of the results of the field application, it can be concluded that the model fits well with actual production and the application of this model can improve the accuracy of well test interpretation.