Organic polymers are commonly used to control filtrate loss in water-based drilling fluids both in circulating and non-circulating periods during drilling operations. In Nigeria, the over dependence on these polymers to achieve this function of drilling fluid is worrisome on the overall well drilling cost. Therefore, a substitute for these polymers with locally available materials is indispensable. In lieu of this fact, an agro by-product, rice husk was evaluated as a possible filtration loss control additive in water-based drilling mud and the results compared with sodium carboxymethyl cellulose (CMC) and polyanionic cellulose (PAC) using static fluid loss measurement approach. The results obtained depict that with a concentration of 20g content of rice husk to 350mL mud (about 20lb/bbl) there was a decrease of 64.89% in fluid loss compared to 62.77% and 59.57% for CMC and PAC respectively at a content of 10g per 350mL mud. Additionally, filter cake thickness measurement from the husk showed a decrease of 3.03% and 8.57% respectively when compared to CMC and PAC. Thus, exploitation of rice husk as fluid loss control additive in water-based mud would be a welcome development in the oil and gas industry since its characteristics of high resistance to water penetration and thermal stability would be applicable to deep wells where high temperature is anticipated since CMC and PAC temperatures degrade at this condition.

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Oil-based mud (OBM) was formulated with soybean oil extracted from soybean using the Soxhlet extraction method. The formulated soybean mud properties were compared with diesel oil mud properties. The compared properties were rheological properties, yield point and gel strength, and mud density and filtration loss properties, fluid loss and filter cake. The results obtained show that the soybean oil mud exhibited Bingham plastic rheological model with applicable (low) yield point and gel strength when compared with the diesel oil mud. The mud density measurement showed that soybean OBM was slightly higher than diesel OBM with mud density values of 8.10 lb/gal and 7.98 lb/gal, respectively, at barite content of 10 g. Additionally, the filtration loss test results showed that soybean mud fluid loss volumes, water and oil, were 13 mL and 10 mL, respectively, compared to diesel oil mud volume of 15 mL and 12 mL. Furthermore, the filtration loss test indicated that the soybean oil mud with filter cake thickness of 2 mm had a cake characteristic of thin and soft while the diesel oil mud resulted in filter cake thickness of 2.5 mm with cake characteristic of firm and rubbery. In comparison with previous published works in the literature, the soybean oil mud exhibits superior rheological and filtration property over other vegetable oil-based muds. Therefore, the formulated soybean oil mud exhibited good drilling mud properties that would compare favourably with those of diesel oil muds. Its filter cake characteristic of thin and soft is desirable and significant to avert stuck pipe during drilling operations, meaning that an oil-based drilling mud could be formulated from soybean oil.

Several correlations have been developed to predict wellhead pressure–production rate relationship in the Niger Delta region. Regrettably, most of these correlations were developed from field data that are not from the Niger Delta region and with limited field test data ranges, so their predictions are lower than expected field values when applied to the Niger Delta. Additionally, some developed wellhead pressure–production rate correlations based on Niger Delta field data are made using in-house equations by the operating companies in the Niger Delta region. To ameliorate this anomaly, sixty four (64) field test data: choke size (S), production rate (q), gas-liquid ratio (GLR), flowing wellhead pressure (Pwh), flowing temperature (FTHP) and basic sediment and water (BS&W) were collected from oil producing wells in the Niger Delta region to develop wellhead pressure–production rate correlations based on Gilbert correlation and modified Gilbert equations. The developed correlations using Niger Delta field test data were compared with several authors' correlations. The results obtained indicate that the developed correlations resulted in better predictions than earlier correlations. In addition, the statistical analysis of the developed correlations used to ascertain the extent of their predicted values differ from the field test data and resulted in average error, absolute error and standard deviation of −0.1477, 0.4430 and 0.9582 for Gilbert formula and −0.2515, 0.4737 and 1.0997 for modified Gilbert formula, respectively. Furthermore, the developed correlations are comparable with an average correlation coefficient of 0.9869. Therefore, the developed correlations can be used as a quick tool to estimate the wellhead pressure–production rate relationship in Niger Delta oil fields.

In the exploration for hydrocarbons, a successful drilling operation to the desired depth hinges on the effective performance of the formulated drilling fluid. Apart from carrying drill cuttings to the surface, another major function of the fluid is to seal off the walls of the wellbore to prevent fluids from coming into and out of the wellbore while drilling a well. Numerous commercial fluid loss additives: carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), among others have been in existence with their drawbacks and effect on the total drilling cost. This study evaluates the use of locally sourced materials: Detarium microcarpum, Brachystegia eurycoma and rice husk, as fluid loss control additive in the water-based drilling fluid. The materials were prepared, ground and sieved to 125 microns. Four sets of water-based drilling muds were formulated using the local materials and CMC as fluid loss control additives. The mud formulation was based on the American Petroleum Institute (API) standard of 25g bentonite to 350mL of water. Also, the filtration test of the formulated muds was performed using API recommended practice for static filtration test at low temperature-low pressure (LTLP) condition. The results obtained showed that Detarium microcarpum and rice husk fluid loss volume and filter cake thickness were comparable with that of CMC from additive content of 10g, while Brachystegia eurycoma was comparable from additive content of 15g. Furthermore, the composite additive results indicated that Detarium microcarpum-rice husk at 95% Detarium microcarpum-5% rice husk performed better than Brachystegia eurycomarice husk of the same combination. Additionally, the fluid loss volume and filter cake thickness of Detarium microcarpum-rice husk additive were comparable with CMC from 10g content. Also, the results revealed that the fluid loss volume and filter cake thickness obtained from the locally sourced materials were within API specification for fluid loss control agents. The mud filter cake characteristics exhibited by these materials depicted that they have slippery, smooth and soft mud cakes; thus, the characteristics of a good mud cake that will prevent differential pipe sticking.

In petroleum industry, oil production strategy to circumvent water coning in reservoirs with strong water drive is quit challenging. To ameliorate this oil production related problem, several water coning prediction models and control approaches have been developed by researchers. The prediction approaches include analytical, empirical and numerical approach. The analytical and empirical prediction approaches are qualitative water coning prediction approach with limited field scale application. However, these approaches model predictions can gain field application if upscale. Numerical approach has provided the fulcrum to study the complexity of water coning phenomenon in bottom-water drive reservoirs, and its prediction and sensitivity results have found wide field application. In addition, the various developed water coning control methods: downhole oil-water separation (DOWS), downhole water sink (DWS), downhole water loop (DWL), among others have proved to be effective, as it reduces the water-cut, produced water and water handling

The prediction of production performance in naturally fractured reservoirs is dependent on reinfiltration and capillary continuity phenomena. In fractured reservoirs, reinfiltration and capillary continuity phenomena have been the major setback during gas-oil gravity drainage. The oil contained within the matrix of the gas invaded zone begins to drain down into the fracture system and into the lower matrix blocks, due to the force of gravity. Some of the oil that is drained out of the upper matrix blocks can reinfiltrate into the lower matrix blocks from the top or side surfaces and can flow down through the areas of contact between blocks. To evaluate the effect of reinfiltration in gravity drainage mechanism and fractured reservoir parameters: fracture width (b f ) and storativity capacity () on reinfiltration process, a fractured porous media was modeled with ECLIPSE-100 Simulator. The base-case simulation runs (SIM-1 and SIM-2) showed that 55.14% and 53.40% of the oil in-place in the modeled fractured porous media were recovered by gas-oil gravity drainage mechanism without reinfiltration and with reinfiltration, respectively. Furthermore, the sensitivity study of the aforementioned fractured reservoir properties on gas-oil gravity drainage and reinfiltration with simulation runs (SIM-3 through SIM-10) indicate that fracture porosity as well as storativity capacity influence the ultimate oil recovery in naturally fractured reservoirs. Additionally, the fracture width has no influence on gas-oil gravity drainage and reinfiltration in the modeled fractured reservoir. Therefore, gravity drainage recovery mechanism proliferation is affected by oil reinfiltration within the matrix blocks that resulted in 3.173% production reduction. Hence, fracture porosity and storativity capacity are considerable factors in reinfiltration mechanism in naturally fractured reservoirs.

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