![]() ![]() Chapter 8 describes the surface flow system, flow in horizontal pipes, and flow in horizontal wells. Chapter 7 covers the flow of fluids to the surface. Chapter 6 deals with the condition of the near-wellbore zone, such as damage, perforations, and gravel packing. Chapter 5 deals with complex well architecture such as horizontal and multilateral wells, reflecting the enormous growth of this area of production engineering since the first edition of the book. Chapters 2–4 present the inflow performance for oil, two-phase, and gas reservoirs. This textbook offers a structured approach toward the goal defined above. This textbook is aimed at providing the information a production engineer needs to perform these tasks of well performance evaluation and enhancement. Remedial steps can range from well stimulation procedures such as hydraulic fracturing that enhance flow in the reservoir to the resizing of surface flow lines to increase productivity. With diagnostic information in hand, the production engineer can then focus on the part or parts of the flow system that may be optimized to enhance productivity. The production engineer has three major tools for well performance evaluation: (1) the measurement of (or sometimes, simply the understanding of) the rate-versus-pressure drop relationships for the flow paths from the reservoir to the separator (2) well testing, which evaluates the reservoir potential for flow and, through measurement of the skin effect, provides information about flow restrictions in the near-wellbore environmental and (3) production logging measurements or measurements of pressure, temperature, or other properties by permanently installed downhole instruments, which can describe the distribution of flow into the wellbore, as well as diagnose other completion-related problems. In summary, well performance evaluation and enhancement are the primary charges of the production engineer. Improving well deliverability by optimizing the flow system from the bottomhole location to the surface production facility is a major role of the production engineer. The VFP change in Figure 1-7 shows that the flowing bottomhole pressure may be lowered by minimizing the pressure losses between the bottomhole and the separation facility (by, for example, removing unnecessary restrictions, optimizing tubing size, etc.), or by implementing or improving artificial lift procedures. While the IPR remains the same, reduction of the flowing bottomhole pressure would increase the pressure gradient ( p – p wf) and the flow rate, q, must increase accordingly. Increasing the drawdown ( p – p wf) by lowering p wf is the other option available to the production engineer to increase well deliverability. In reservoirs with pressure drawdown-related problems (fines production, water or gas coning), increasing the productivity can allow lower drawdown with economically attractive production rates, as can be easily surmised by Equation ( 1-6). Finally, more favorable well geometry such as horizontal or complex wells can result in much higher values of J D. Thus, stimulation can improve the productivity index. A negative skin effect can be imposed if a successful hydraulic fracture is created. For example, the skin effect can be reduced or eliminated through matrix stimulation if it is caused by damage or can be otherwise remedied if it is caused by mechanical means. The concept of the dimensionless productivity index combines flow geometry and skin effects, and can be calculated for any well by measuring flow rate and pressure (reservoir and flowing bottomhole) and some other basic but important reservoir and fluid data.įor a specific reservoir with permeability k, thickness h, and with fluid formation volume factor B and viscosity μ, the only variable on the right-hand side of Equation ( 1-6) that can be engineered is the dimensionless productivity index. The terms steady state, pseudosteady state, and transient will be explained in Chapter 2.
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