Over the years, interference test analysis has become a veritable analytical tool in reservoir characterization of most brown fields. At interference the area between the wells has been adequately swept. Therefore, results obtained from interference data analysis show a better reservoir representation as compared to that obtained from single well test. This study presents an analysis of interference test data of horizontal and vertical wells for various well spacing using Malekzadeh's model. Malekzadeh assumed an isotropic reservoir condition. For the fact that anisotropy has a major effect on the pressure transient responses of horizontal well, the results of Malekzadeh have limited applicability. Thus, in an attempt to alleviate this limitation, this analytical study was borne. The reservoir model used in this study is assumed to be anisotropic, laterally infinite and bounded at its top and bottom. Skin and wellbore storage effects are not considered. For proper analysis, three cases are considered: (1) an observation horizontal well and active vertical well, (2) observation vertical well and (3) active horizontal well and an active observation vertical well and an active horizontal well. Type curves are generated for each case. Our results show a slope of 1.1513/cycle for Cases 1 and 2 and a slope of 2.303/cycle for Case 3 at interference for late time flow regime. However, a check on the effect of anisotropy reveals that directional permeabilities bring about a slightly higher bottomhole responses for late-time flow regimes. For pressure to be felt by adjacent wells, an enomous time is sometime needed pending on the location of the observation well. In conclusion, our findings show that anisotropy strongly affects interfering pressures between wells.

An oil-based drilling fluid system was formulated using rubber seed oil as base oil. Rubber seed oil was chosen because its aniline and flash points fall within the range of oils used as base oil. It is also locally available and easily affordable. The rheological (flow) properties of the rubber seed oil-based drilling fluid system were measured and results obtained show that the 10-sec and 10-min gel strength values for the formulated mud are 210lb/ft2 and 211lb/ft2 respectively while the mud density, plastic viscosity and yield point values are 10.60ppg, 1cP and 328lb/ft2 respectively. Comparison with the properties of a commercial oil-based drilling fluid show that the formulated mud has a high penetration rate and hole cleaning ability and so is effective in drilling operations although some disadvantages were observed.

The use of dimensionless pressure and dimensionless pressure derivative type curves has fully overcome the challenges experienced in the use of straight line methods and has brought about major successes in well tests analyses. Flow periods and reservoir boundary types are easily delineated and identified with the use of these curves. Furthermore, near wellbore characterization results are now more reliable. In this study, type curves for a reservoir subject to bottom water energy and a vertical well completion are developed to reveal specific signatures that can be used to achieve efficient pressure test analysis. Both early and late flow periods were considered for a wellbore of negligible skin and wellbore storage influences. Results obtained show that dimensionless pressures depart from infinite-acting behavior and attain steady state at dimensionless time of order proportional to the square of dimensionless reservoir thickness. Wellbore dimensionless radius affects dimensionless time of attainment of steady state inversely, which is rather accelerated by large fluid withdrawal rates (large pressure drawdown). On the other hand, dimensionless pressure derivatives show gradual collapse to zero after expiration of infinite flow. The rate of collapse is strongly affected by wellbore properties and pressure drawdown. Radial flow is generally characterized by a constant slope of 1.151 during which period the dimensionless pressure derivative gave a value of 0.5. Following assumption of negligible wellbore skin and storage, no early time hump is observed on dimensionless derivative curves.

Water production in an oil well is undesirable both economically and environmentally. Therefore water arrival pattern into a well has to be understood clearly where a reservoir is surrounded by an aquifer. However, predicting the breakthrough time of water in a producing well has been a controversial issue and a major challenge to petroleum engineers. This paper investigates water arrival pattern into a vertical well completed in reservoir with double-edge water external lateral boundaries to be able to understand important factors affecting water breakthrough. Water breakthrough time is the time it takes for the first droplet of water cut to reach the wellbore under the prevailing production rate regime. This marks the end of the production of clean oil from the well. Once the breakthrough time is approached, depending on the strength of the external boundary (supplying aquifer) the pressure responses in the reservoir first attain a steady state condition. Further production then leads to steady rise in produced water-oil ratio. Real time dimensionless pressure distribution, using appropriate source functions for a vertical well in a reservoir with double-edge water as its lateral external boundaries was utilized for the study. Well responses were computed for a wide range of reservoir, wellbore and fluid properties. Results show that water breakthrough time is strongly affected by the lateral distance of the external edge water from the perforations according to the relation tDx2eD/π2(kh/ kv). Not too far edge water would yield earlier breakthrough than far away edge water for a well completed in an isotropic reservoir. In a largely horizontally anisotropic reservoir therefore, water breakthrough may be delayed if the water from the edges respond unequally to a production transient in the well. For a reservoir with reasonable horizontal isotropy, only central well location may delay water breakthrough. If this does not yield the desired delay, then the perforation should be located farther vertically above the points opposite to the pay zone.

If a well loses it producing potential before depletion, then the pressure analysis of the well system should be carried out to ascertain the cause. Nodal analysis, is one of the analysis methods which is aimed at analysing pressure distributions across different nodes. This analysis will serve as a guide to revamping the well. This paper utilizes nodal analysis simulation approach to study the cause of pressure drop in a well system. Inflow performance relation (IPR) and vertical lift performance (VLP) were used to determine the pressure distribution in the well attainable at various flow rates and wellbore condition. Results show that nodal analysis method can be used to obtain prevailing well bottom hole pressures at various flow rate, the flow rates responsible for a unit pressure drop in a well system, the pressure loss across perforation and tubing using IPR and VLP of the well system respectively. Well completion strategies are adequately advisable from application of nodal analysis.