Modified reservoir quality indicator methodology for improved hydraulic flow unit characterization using the normalized pore throat methodology (Niger Delta field as case study)

The detailed characterization of complex reservoir units, typical of the thin-bedded canyon turbidites system within the clastic environment is essential for accurate reservoir modelling. The sedimentary architecture usually overprinted by late diagenesis results in the intrinsic complexities which poses major problems in modelling these systems. Although the average permeabilities exhibited by most clastic reservoirs is relatively high, the low permeabilities of the component shale strata results in low sweep efficiency and transmissibilities, and may form effective flow baffles. Recent advances in petrophysical modelling and formation evaluation studies demonstrate the applicability of normalized pore throat radius Rtot methodology for improved reservoir characterization and production optimization in challenging systems.This paper presents a modification of the reservoir quality indicator (RQI) methodology for hydraulic flow unit characterization using the normalized pore throat concept. Result of the analysis for the various genetic reservoir units demonstrates an improvement with a correlation coefficient of 78% for the proposed modified RQI over 31% for the existing RQI method in defining the unit slope line for the Channel Storey Axis unit. In addition, regression analysis between the irreducible water saturation from mercury injection capillary pressures and FZI depicts a higher correlation coefficient of 76% for the modified RQI over 64% for the existing method. The higher correlation coefficient indicates an improved efficacy of the proposed model for hydraulic flow zone characterization. The efficacy of the proposed methodology was also validated with a numerical flow simulation model. This demonstrates improved efficient for reservoir characterization studies

A Simple Model to Predicting Pore Pressure from Shear Wave Sensitivity Analysis

A successful seismicity alongside core analysis provides data for subsurface structural mapping, definition of lithology, identification of the productive zones, description of their depths and thickness. Inadequate understanding of Pore pressure of a formation is regarded as one of the major problems drillers face in the exploration area. This may be amongst others, the pressure acting on the fluids in the pore spaces of the rock. Pore pressure can be normal, abnormal or subnormal. Shear waves are slow and thus, get to the surface after primary wave. It is with this intrinsic property that this project was initiated and researched. Data was obtained from a major operator in the Niger Delta. Methods of this study are as follows: Log description, interpretation and analysis and evaluation of pore pressure using the petro-physical parameters, model development using Domenico's equation as foundation and the shear wave velocity estimation. The result from this study, shows the importance of well logs and shear wave velocity in the evaluation of pore pressure, it also indicates where pressure can be encountered during drilling activities

Pore Pressure and Fracture Gradientassessment from Well Log Petrophysical Data of Agbada Formation, South-East Niger-Delta

Changing down-hole conditions observed during hydrocarbon exploration can be divers. Some desired ones concern oil/gas shows while others may vary from borehole/drilling fluid association and pressure situations. Managing pressure variations and geopressure zones while drilling has been an issue of concern which has yield generic positive results over the years. However pre-pressure zones (i.e. zones above pressure zones), can display characteristics that are worthy of note in view of the underlying rock potential. Pore pressure and fracture pressure has been evaluated using Eaton’s equations amongst others on data for some reservoir of Agbada formation in the petroliferous Niger Delta. This is in view of knowing the potential of this pre-pressured zone with effective porosity and water saturation necessitated by production operations and well re-entry processes. These computations adopted various pressure models and have yielded good result presented as plots. It was observed that depth of rock units is the main indicator of rock shrinkage leading to increase in fracture due to increase in production and hydraulic fracturing. Adequate attention must be paid to the integrity (density) of the explored formation as they become sandwiched with under-compacted argillaceous sediments

Well Placement Optimization Using a Basic Genetic Search Heuristics Algorithm and a Black Oil Simulator

In petroleum reservoir management, the essence of well placement is to develop and maintain reservoir pressure in order to achieve maximum production for economic benefits. Large production can be achieved with the placement of multiple wells but this approach is capital intensive and inefficient for the development of a reservoir. A preferable option is the optimal placement of production and injection wells so as to fully capitalize on the imbedded hydrocarbons at a relatively decreased capital investment. The aim of this study is to use developed algorithm and a black oil simulator to place wells in the zones for optimal recovery in the reservoir. Optimal production was determined out of eight scenarios created from well placement in a hypothetical reservoir (finch reservoir) using a black oil simulator, alongside an algorithm developed with java for determining the best possible locations for well placement, taking into consideration the reservoir permeability, fluid saturation, and pay zone thickness. The results of this study reveal that well placement using the engineering judgment coupled with the application of the algorithm using a black oil simulator results in better production compared to other scenarios which consider the combined effect of algorithm and black oil simulator alone

Coal mining and the environmental impact of Acid Mine Drainage(AMD): A review

In spite of the growing global initiatives towards achieving clean energy, coal remains a dominant source of electricity generation, a fuel for iron and steel production, an important entity among road construction materials and a commodity for foreign exchange earnings for many nations. Coal mining from old and active sites remains a source of an environmental problem described as acid mine drainage (AMD). AMD is produced when sulfide present in waste rocks or tailings in coal mines reacts with air and water in a microbes facilitated oxidation to form solutions with high acidity. The acids formed by these chemical and biological conditions further release heavy metals present in the host rock in concentrations higher than are acceptable by environmental standards (pb;0.01, Zn;5, Cu;2, Fe;0.3 mg/l as prescribed by WHO and Encyclopedia of Environmental Science,2000) such that soils, surface and underground waters are contaminated. Consequently, the human population which derives her livelihood in the mine zones, in form of crop production and fishing/modern aquaculture is endangered by terminal health diseases. This article aims at bringing forth, the urgent need to work towards achieving goal six of the United Nations Sustainable Development Goals, 2030 (SDGs-6) which is clean water and sanitation while enriching the knowledge repository of the environmental problem for the purpose of teaching, research, community services and policy making. An overview of AMD menace, variables which influence its formation, selected areas that have been impacted, and a brief analysis of its treatment cost have been discussed with a list of concluding remarks in the paper. Keywords: Coal, Mining, Environmental , AM

A New Solution Methodology to the Material Balance Equation, for Saturated Reservoirs

The material balance equation (MBE) is a versatile analytical tool in petroleum reservoir engineering. Solution to the MBE is put to a predictive use for predicting reservoir performance, i.e. cumulative oil production, Np as a function of the declining average reservoir pressure, . For under-saturated reservoir (single-phase flow), the MBE presents Np as an explicit function of pressure drawdown ; hence a direct solution of the MBE yields the average pressure, for a given Np value. However, for multiphase flow in saturated reservoirs, the average reservoir pressure does not appear explicitly in the MBE, rather, it is implicitly present in the various pressure-dependent PVT parameters in the MBE (i.e. (Bo, Bg and Rs). Furthermore, the MBE for saturated reservoirs features the cumulative GOR term, Rp, a parameter related to Np; hence solving the MBE for saturated reservoirs typically involves cumbersome iterative schemes. There exist in the literature various methodologies of solving the MBE with the purpose of predicting estimates of cumulative oil production, Np versus the declining average reservoir pressure, . The methodologies typically involve some multi-step iterations as the equation is solved for Np or Gp at various arbitrarily-chosen pressure nodes. The need to solve this implicit problem without the rigor of human guesswork is the motivation for this work. This current work therefore presents a simple and computationally-cheap method for solving the MBE for the purpose of predicting estimates of cumulative oil production, Np versus the declining average reservoir pressure, . In this new solution methodology, the philosophy of solving the MBE is analytically founded on the equality of the Left Hand Side, LHS (fluid withdrawal terms) and the Right Hand Side, RHS (fluid expansion terms) of the MBE for saturated reservoirs, and the pressure that upholds the equality. This new solution methodology has been applied to two reservoir models and has been found to yield performance predictions that compares excellently well with predictions obtained from numerical solution (simulation) of complex fluid flow equations

Modelling the Effect of Composition Change during Condensate Dropout in a Horizontal Gas Well.

This paper presents a mathematical model describing the behavior analysis for a two-phased gas-condensate system narrowing down on the three zone method. The three zone method accounts for the composition change in the reservoir and is based on modeling the depletion by three main flow regions: • A near wellbore region (Region 1) where the oil saturation is important allowing both phase, vapor and liquid to be mobile. • Region 2 where condensate and gas are present but only the gas is mobile. • An outer Region 3 exists when the reservoir pressure is greater than the initial gas dew point and contains only gas. This research proposed a fourth region (Region I) which is the immediate vicinity of the well where accumulation of liquid buildup at high rates which yielded from an increase of liquid saturation and a probable decrease in gas relative permeability. The existence of the fourth region or flushed zone is particularly important as it represent the total skin effect: mechanical skin, rate dependent two-phase skin and skin due to gas condensate blockage. The calculated well deliverability rate using the modeled equation for gas condensate reservoir showed a relatively high difference when compared to other known equations. This significant difference is as a result of the effects of the proposed Region I. The developed correlation confirms that as the pressure drops below dew point there occurs condensate banking which when the critical saturation is reached becomes mobile and leads to a reduction in gas flow rate in the reservoir

A Review on Gas Well Optimization Using Production Performance Models—A Case Study of Horizontal Well

This study considered the solution methods to determine optimal production rates and the rates of lift gas to optimize regular operational objectives. The foremost tools used in this research are offered as software platforms. Most of the optimization hitches are solved using derivative-free optimization based on a controlled well Performance Analysis, PERFORM. In line with production optimization goal to maximize ultimate recovery at minimum operating expenditure, pressure losses faced in the flow process are reduced between the wellbore and the separator. Nodal analysis is the solution technique used to enhance the flow rate in order to produce wells, categorize constraints and design corrective solution. A hypothetical case is considered and sensitivity analysis using the IPR Models for horizontal gas wells provides the effect on pressure and liquid drop out. The gas lift method is economically valuable as it produced an optimal economic water cut of 80 percent with 2 - 4 MM scf/day rate of gas injection; thus, 1800 - 2000 STB/day gas was produced