Gas compressibility factor, also known as gas deviation factor or Z-factor, is a thermodynamic correction factor which describes the deviation of a real gas from ideal gas behaviour. The, free gas Z-factor in the Material Balance Equation (MBE) of single-porosity gas reservoirs with insignificant rock (matrix) compaction (after pressure depletion) does not reflect cases in low-permeability gas reservoirs having remarkable rock compaction. Through gas MBE modifications, previous researchers developed Z-factors for dual-porosity (fractured) low permeability gas reservoirs by incorporating gas desorption; however, their approaches create complexity for routine calculations. Therefore this study was designed with the purpose of deriving a free gas Z-factor for single-porosity low-permeability gas reservoirs and further modifying it for more simplicity and accuracy in a dual-porosity scenario. The free gas Z-factor derived for single-porosity low-permeability gas reservoirs is expressed as:  where , , , ,  and  are single-porosity Z-factor without rock compaction at pressure , water compressibility, initial water saturation, matrix compressibility, initial gas saturation and pressure depletion, respectively. However, the developed dual porosity free gas Z-factor model incorporates ratio of dual porosity to initial matrix porosity, and it is expressed as:    where  and  are initial matrix porosity and fracture porosity, respectively. The Z-factor model was graphically and statistically correlated with an existing free gas Z-factor model for dual porosity reservoirs. For all the hydraulically fractured shale gas formations considered, the correlations yield R2 values of 1.000.

Enhanced oil recovery (EOR) techniques are considered due to unimpressive oil recovery, limited oil reserves, and non-applicability of primary recovery methods in some (heavy oil) fields. In Nigeria, preparation is in gear towards implementing EOR projects. This paper therefore reviews the global trend of EOR practices and discusses Nigeria’s present status, prospects, and challenges. Most EOR projects are employed in sandstone (high permeability) reservoirs; hence based on lithological considerations, all EOR methods are feasible in Nigeria. However, miscible hydrocarbon gas injection is found to be a very good EOR choice because it would drastically reduce the uneconomical practice of gas flaring; besides, transportation of carbon dioxide (CO2) and flue gas is virtually non-existent in Nigeria. Chemical (especially surfactant) flooding is costly; hence it would be feasible in Nigeria if oil price is high. At present, cost implications of heat treatment facilities may be an impedance to implementing thermal EOR for heavy oil in Nigeria. Though microbial EOR is the cheapest, it is not favorable in high temperature (above 85 oC), high salinity (above 100,000 ppm) and deeper (beyond 3,500m) reservoirs. For EOR practices to thrive in Nigeria, there should be an extensive economic evaluation and forecasting, effective research and development, effective training of technical staff for proper operation, surveillance and maintenance of EOR projects, implementation of health, safety and environmental (HSE) guidelines, low inflation rates, low interest rates on loans, general price stability, favorable tax policy, low import duties on machineries and equipment used for EOR, modified private market decisions and encouraging legal and regulatory framework.

In this study, an ablative pyrolyser having 27.1 cm inner diameter, 41.2 cm outer diameter, the full chamber height of 74.7 cm and chamber volume of 40 litres was designed and fabricated. 150KW heater was wounded around the reactor chamber made of stainless steel to provide a higher temperature of up to 1400 °C. The -40 to 105°C capacity heat resistance wires were used to conduct the heater into the electrical panel which has several components such as the contactor, temperature controller, thermocouple wire and so on to give a particular desired working temperature. This pyrolyser applies technology of thermal energy in the heated walls of the pyrolyser being transferred to the biomass by conduction in the absence of oxygen for onward disintegration into gas, bio-oil, and biochar. After fabrication, 12 kg each of Tectona grandis and Rhopalosiphum maidis was fed into the reactor and pyrolyzed at 500 °C, the bio-oil product for both samples were mixed together and distilled at 120 °C and the bio-oil distillate was characterized for density, kinematic viscosity, pH, acid value and free fatty acid content. The bio-oil distillate shows a density of 0.960 g/cc, pH of 7.2, kinematic viscosity of 84 cst and acid value of 42.20 compared to the bio oil crude which showed higher values. This pyrolyser has been found on average to melt 12 kg each of Tectona grandis and Rhopalosiphum maidis to 5353 and 3493 g crude bio-oil respectively for a period of at least 3 h. The mass of bio-char for tectona grandis and Rhopalosiphum maidis were 3325 and 2614 g respectively while the reactor requires 8 h to cool before discharging the bio-char from the reactor. This research work can provide a basic designing formula for effective and workable ablative pyrolyzer fabrication for Nigerian wastes having high energy content.

The analysis of well test data for deviated wells penetrating layered reservoirs is usually a challenging problem due to the complexity of interlayer flow within reservoirs. These problems are as a result of insufficient data from unique layer flow into the wellbore. The aim of this work is to present a new analytical pressure-transient solution for deviated wells (0° ≤ w  ≤ 12°) in layered reservoirs with crossflow. The individual layer skin property was also investigated. Green's function for the layered system was obtained by Laplace transformation and double Fourier cosine transform. The wellbore was discretized into several segments and each segment was treated as a uniform flux source, a linear system was set up and the pressure drop solution was obtained in the Laplace space and transformed back to the real space. The nonlinear parameter estimation method was applied as a means to determine the layered skin. Applying the model to field data obtained from published works; the pressure derivative curves indicated that the early-time behaviours of reservoirs are totally different even with little change in well inclination (except the bottom boundary is set as constant pressure), but late-time behaviours (radial flow) are very similar for all the cases. The results also showed that early time pressure drop in commingled reservoirs is much higher than that of cross-flow reservoirs, because the wellbore sees the boundary

Different gas equilibrium adsorption models (or isotherms) with various theoretical frameworks have been applied to quantify adsorbed volume (V) of gas (or fluid) through pressure-volume behaviour at a constant temperature. Most often, Langmuir isotherm (representing Type I Isotherm) has been used in modelling monolayer adsorption even though it yields over-estimation at higher pressures thus contradicting the description of Type I isotherm. Here, higher pressures refer to pressures above the adsorption saturation pressure(Ps) . Hence, in this work, a new Type I adsorption isotherm involving pressure(P), adsorption saturation pressure(Ps) , maximum adsorbed volume  and adsorbate-adsorbent resistance parameter  was developed using kinetic approach. The developed adsorption isotherm is V=  and it shows that Vmax is attained when pressure increases to Ps , above which no further gas adsorption occurs. The developed isotherm can be used to model all cases of monolayer adsorptions of gases (or fluids) on adsorbents. The developed and Langmuir isotherms were used in modelling secondary low-pressure gas adsorption data of different adsorbents and the qualities of fit were statistically assessed. For laboratory methane adsorption on Turkey’s shale sample at 25°C, the developed isotherm yields a correlation with an R2 value of 0.997 and predicts a maximum adsorption volume of 0.0450 mmol g-1 at a Ps  of 2,005 psia. However, Langmuir isotherm yields a correlation with an R2 value of 0.989 and predicts a maximum adsorption volume (Langmuir volume,VL ) of 0.0548 mmol g-1 at infinite Ps. At the higher-pressure range, the developed isotherm reveals that Langmuir isotherm is not a Type I isotherm but a "pseudo-Type I” isotherm.