This work enables accelerated fluid recovery in oil and gas reservoirs by automatically controlling fluid height and bottomhole pressure in wells. Several literature studies show significant increase in recovered oil by determining a target bottomhole pressure but rarely consider how to control to that value. This work enables those benefits by maintaining bottomhole pressure or fluid height. Moving Horizon Estimation (MHE) determines uncertain well parameters using only common surface measurements. A Model Predictive Controller (MPC) adjusts the stroking speed of a sucker rod pump to maintain fluid height. Pump boundary conditions are simulated with Mathematical Programs with Complementarity Constraints (MPCCs) and a nonlinear programming solver finds a solution in near real-time. A combined rod string, well, and reservoir model simulate dynamic well conditions, and are formulated for simultaneous optimization by large-scale solvers. MPC increases cumulative oil production vs. conventional pump off control by maintaining an optimal fluid level height.
When a shale gas reservoir is being developed, two fundamental questions need to be answered: (1) how much gas is in place and (2) how much gas can be produced when reservoir is depleted to a specific pressure. This paper examines the pore size distribution impact on gas volume in place during reservoir depletion. A calculation procedure for a multiple component system will be presented with an illustration using Barnett core mercury injection data.Literature suggests that a monolayer adsorption model is not sufficient for shale gas reservoirs with multiple components in volumetric calculations. In this paper, we propose to use the cylindrical Simplified Local Density model with Peng-Robinson Equation of State (SLD-PR EOS) to solve the local hydrocarbon density distribution for gas in micro-and meso-pores. The integration of the local density over the pore width yields an average density. Pore size distribution (PSD) data such as mercury injection provide the pore volume contribution of different pore radii. Coupling the pore volume distribution with the calculated average density, we calculate the gas in place due to pressurization and adsorption under different pressures. The recovery from the shale reservoir is determined by repeating the process at different pressures. Because of the high non-linearity of the SLD-PR EOS, a trust-region optimization algorithm has been used to solve the local density profile.Pore size distribution has a tremendous impact on the gas storage capacity of a shale formation. Results from this study reveal that neglecting PSD can yield more than 40% errors for original gas in place (OGIP) calculation. Incremental pore volume is modeled with a Log-Gamma distribution for the Barnett field. OGIP sensitivities to the distribution parameters are also investigated. For the same porosity under the same ambient pressure and temperature, more small pores indicate more gas in place. Therfore under the same depletion process, more recovery can be expected from small pores. This paper utilizes MICP data for a Barnett gas shale core sample to demonstrate the calculation procedure for implementing core data, fluid characterization, and SLD -PR EOS modeling to calculate original gas in place. This paper has the following two novel points: (1) An improved OGIP calculation procedure for multicomponent gas shales is proposed using the cylindrical form of the SLD-PR EOS model and MICP data from core samples; (2) PSD has a tremendous influence on OGIP values in shale formations because of the presence of micropores and neglecting PSD can yield significant errors in OGIP values.
Subsea processing is an evolving technology in response to ultradeepwater hydrocarbon development and has the potential to become one of the most attractive methods in the oil industry to economically unlock hydrocarbon resources. The objective of this paper is to examine the features of subsea fluid-processing technologies and capabilities, and compare the advantages and disadvantages of different facility types. The advantage of subsea processing systems is that they allow fluids to be boosted from longer tieback distances. Constraints associated with subsea processing systems include operation efficiency, produced-waterand sand-handling capabilities, and the system's ability to handle hydrates/scale. In this paper, we reviewed the application of subsea systems in 12 deepwater fields and discussed the significance of each. Furthermore, future subsea-technology development and anticipated challenges are outlined in this paper. The significance of this study is to summarize the lessons learned from current available uses so that future decisions regarding the application of these subsea processing technologies can be made appropriately and efficiently.
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