An increased awareness of drilling costs amidst the volatile nature of the market has necessitated pushing the frontiers of drilling technology to improve efficiency thereby saving costs. It is in view of this trend that the concept of drilling using a downhole pulsating device was conceived. This method sought to optimise drilling performance by manipulating two drilling parameters; the weight on bit and transient hydraulic fluid effects in order to obtain an empirical model for subsequent simulations which Consist of includes a pilot well drilled on paper. The downhole pulsating device is fitted in the bottomhole assembly and primarily comprises of two valve plates sitting flush against each other. The bottom plate is static in the wellbore allowing fluid to pass through its centre while the top valve is rotated around the wellbore circumference by the rotor of the mud motor, thus constraining the flow in the flow path. Transient hydraulics generates pulses which impact on the drilling performance and it has been proven to enhance the rate of penetration.It was noted that there is a momentary underbalance as the downhole pulsating device undergoes through a complete opening cycle. Hence there is a need to use a rotating head to secure the well. A further advantage of this method is economically viable and it is only requires fitting the downhole pulsating device through a sub into the drill string.A model of fluid flow across a downhole pulsating device was generated using a two parameter, second degree polynomial equation, which includes the force generated and transferred to the bit, and the opening ratio of the downhole pulsating device within a unit time interval. It was also demonstrated that drilling with a downhole pulsating device exerts more hydraulic horsepower on the drill bit and provides better cleaning for the bit.

Summary Maximizing oil recovery in thin and ultrathin (less than 30 ft) oil columns is a challenge as a result of coning or cresting of unwanted fluids into the wellbore in both vertical and horizontal wells. There is considerable oil left behind, above the well completion in the reservoir. This may also occur in horizontal wells when bottom- or edgewater encroachment or invasion takes place. The development of the gas resources from these reservoirs is a major challenge because regulators want an optimal development plan for the oil rim before project approval is made. This can delay upstream gas supply to liquefied-natural-gas (LNG) projects and grind down project value. A smart development strategy has been proposed for the development of these challenging reservoirs. This involves the use of intelligent multilateral wells in simultaneous oil and gas development; the first (top) horizontal-lateral-well legs of the multilateral well will be completed at the crest of the reservoir in the gas cap. The second (lower) horizontal-lateral-well leg will be completed just above the gas/oil contact (GOC). Extensive numerical reservoir-flow simulation has been used to demonstrate the ability and possibility of using a single wellbore for simultaneous oil and gas production. This proposed development strategy will provide high impact on the asset of such oil and gas reservoirs by providing a cost-effective-technology solution. The numerical-simulation results show that the intelligent multilateral well will significantly improve the overall cumulative production of gas and oil from a thin oil reservoir with a large gas cap compared with conventional wells and also provide the opportunity for automatic gas lift for low-gravity crude (°API). This paper (1) presents the use of intelligent multilateral wells to produce oil and gas from the same wellbore simultaneously in the thin oil reservoir and (2) provides information on the delay and reduction of excess production of unwanted fluids (water) during oil and gas production from thin oil reservoirs using intelligentwell technology, including cost effectiveness.

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Performance evaluation of miscible and near-miscible gas injection processes is available through conventional finite difference (FD) compositional simulation. Streamline methods have also been developed in which fluid is transported along the streamlines instead of using the finite difference grid. In streamline-based simulation, a 3D flow problem is decoupled into a set of 1D problems solved along streamlines. This reduces simulation time relative to FD simulation, and suppresses the numerical dispersion errors that are present in FD simulations. Larger time steps and higher spatial resolution can be achieved in these simulations. Thus, streamline-based reservoir simulation can be orders of magnitude faster than the conventional finite difference methods. Streamline methods are traditionally only applied to incompressible flow processes. In this paper, the method is adopted and assessed for application to compressible flow processes. A detailed comparison is given between the results of conventional FD simulation and the streamline approach for gas displacement processes. Finally, some guidelines are given on how the streamline method can potentially be used to good effect for gas displacement processes.

Performance evaluation of miscible and near-miscible gas injection processes is available through conventional finite difference (FD) compositional simulation, which is widely used for solving large-scale multiphase displacement problems that always require large computation time. A step can be taken to reduce the time needed by considering low-resolution compositional simulation. The model can be adversely affected by numerical dispersion and may fail to represent geological heterogeneities adequately. The number of fluid components can possibly be reduced at the price of less accurate representation of phase behavior. Streamline methods have been developed in which fluid is transported along the streamlines instead of the finite difference grid. In streamline-based simulation, a 3D flow problem is decoupled into a set of 1D problems solved along streamlines, reducing simulation time and suppressing any numerical dispersion.Larger time steps and higher spatial resolution can be achieved in these simulationsparticularly when sensitivities runs are needed to reduce study uncertainties. Streamline-based reservoir simulation, being orders of magnitude faster than the conventional finite difference methods, may mitigate many of the challenges noted above. For gas injection, the streamlines approach could not provide a high resolution or adequate representation for the multiphase displacement. In this paper, the streamline simulations for both compositional and miscible gas injection were tested, in addition, the conventional gas injection scheme and detailed comparison between the FD simulation and the streamline approachareillustrated. Also, guidelines of how streamline can be potentially used to visualize the effect of gas displacement are presented in this paper.