Comparison and Sensitivity Analysis of Water Saturation Models in Shaly Sandstone Reservoirs Using Well Logging Data (Published)
Shaly sandstone reservoirs have complex pore systems with ultra-low to low interparticle permeability and low to moderate porosity. This has leaded to development of several models to calculate water saturation in shaly sandstone reservoirs using different approaches, assumptions and certain range of conditions for application. This study has used actual well logging data from two different fields of South Texas and North Sea to evaluate and compare the most popular five shaly sandstone models for calculating water saturation. Identification of shale distribution for selection of suitable model is also presented. Furthermore, sensitivity analysis of tortuosity coefficient (a), cementation exponent (m) and water saturation exponent (n) is achieved to investigate their effects on computed values of water saturations using different models.The results indicated that identification of shale distribution is necessary and improper utilization of shaly sandstone models results in drastically erroneous values of water saturation. Therefore, shale distribution in the South Texas field is identified to be mainly laminated with few of structural ones while distribution is dispersed in the North Sea field. The results also showed that the increase of shale volume decreases water saturation calculated for all popular models. In addition, the increase of tortuosity coefficient and/or cementation exponent (m) causes overestimation of water saturation while the increase of saturation exponent (n) results in an underestimation values. The application of the attained results of this study will have real improvement in selection and application of the appropriate shaly model. This provides more accuracy and real improvement in formation evaluation, reserve estimation, reservoir characterization, and consequently in reservoir simulation.
In this paper, sensitivity and duality analyses have been performed on our earlier developed optimal water treatment cost model for Ghana. Linear Programming was used to formulate the model and tested with real data collected from Weija Water Headworks in Accra using Interior-Point Method to obtain solutions. The effects of variations of selected key parameters on the developed model have now been investigated. Marginal costs of water production in the selected water headworks have also been found. It is strongly recommended that all Water Headworks under Ghana Water Company Limited (GWCL) should employ at least one Operations Researcher to assist them in some of these post-optimality analyses.
Sensitivity analysis allows to evaluate how the resulting performance of the project at different values of given variables required for calculation. This type of analysis to determine the most critical variables that have the greatest affect on the feasibility and effectiveness of the project. In this paper we reviewed the concept and essence of the sensitivity analysis and it stages in addition to the study of one of the projects ability to continue using the net present value index NPV. the ranking of the major indices performed in order of importance to the outcome of the project. In other words, the size of the NPV according to the obtained values of the critical point and sensitive edge
The study examined the prevalence of HIV/AIDS in the Techiman Municipality of Ghana. We used model with standard incidence to analyze, model and predict the prevalence of HIV/AIDS in the Techiman Municipality. The model has two equilibrium states: the disease-free equilibrium and the endemic equilibrium states respectively. The stability condition of each equilibrium point is discussed. The basic reproductive number ( ) of HIV/AIDS infection is estimated to be in the Techiman Municipality. Our work shows that the reproductive number of HIV/AIDS infection in the Techiman Municipality is less than 1( ) and therefore concluded that the disease is not epidemic in the municipality as described by the GAC in their study in 2005. We recommend that education on HIV/AIDS in the municipality should be intensified so as to decrease the rate of transmission of HIV in the municipality.