Category: Production From Undersaturated Oil Reservoirs

The presented three inflow performance equations that can be used to analyze the reservoir behavior for single-phase oil production: steady-state, transient, and pseudosteady-state flows. The production engineer selects the most appropriate of these relationships based on the far-field boundary condition for the well of interest. If the pressure, pe, at the drainage boundary can be approximated…

Provided volumetric flow rates of undersaturated oil reservoirs as functions of the permeability, k. This permeability was used as a reservoir property. In reality this is only an approximation, since such a use of permeability is correct only if the flowing fluid is also the only saturating fluid. In such case the “absolute” and “effective” permeability values are…

All well deliverability equations relate the well production rate and the driving force in the reservoir, that is, the pressure difference between the initial, outer boundary or average reservoir pressure and the flowing bottomhole pressure. If the bottomhole pressure is given, the production rate can be obtained readily. However, the bottomhole pressure is a function of the…

Rarely do wells drain regular-shaped drainage areas. Even if they are assigned regular geographic drainage areas, these are distorted after production commences, either because of the presence of natural boundaries or because of lopsided production rates in adjoining wells. The drainage area is then shaped by the assigned production duty of a particular well. To account for irregular drainage…

Earlougher (1977) indicated that the time, tpss, at which pseudosteady state begins is given by where A is the drainage area and tDA has a characteristic value that depends on the drainage shape. For a regular shape such as a circle or a square, the dimensionless time at the onset of pseudosteady state, tDApss, is equal to 0.1. For a well…

Almost all wells eventually “feel” their boundaries. In Section 2-2 the steady-state condition implied a constant-pressure outer boundary. Naturally, this boundary can approximate the impact of a larger aquifer. Induced constant pressure may be the result of injector–producer configurations. For no-flow boundaries, drainage areas can either be described by natural limits such as faults, pinchouts, and so…

The diffusivity equation describes the pressure profile in an infinite-acting, radial reservoir, with a slightly compressible and constant viscosity fluid (undersaturated oil or water). This equation, with similar expressions in wide use in a number of engineering fields such as heat transfer (Carslaw and Jaeger, 1959), has the classic form Its generalized solution is where Ei(x)…

Steady-state performance means that all parameters, including flow rate and all pressures, are invariant with time. For a vertical well draining a region with radius re, this requires that the pressure at the well boundary, pe, and the bottomhole flowing pressure, pwf, are constant with time. Practically, the boundary pressure, pe, for a production well can remain constant only…

Well deliverability analysis predicts the wellbore flowing pressure for a given surface flowrate. Deal with well inflow performance and describe the reservoir variables that control well productivity under different conditions. Wells drilled in oil reservoirs drain a porous medium of porosity ϕ, net thickness h, and permeability k. To understand the process of flow from the reservoir and into…