Degree

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

Document Type

Dissertation

Abstract

Pressure transient analysis (PTA) is one of the most robust and commonly interpretation tools available for reservoir characterization. Common applications of PTA include estimation of near-wellbore and reservoir properties, detection of reservoir limits and identification of depletion mechanisms. In addition, PTA allows the identification of sealing and leaky faults and the characterization of its properties, such as permeability and transmissibility hence direction of leakage within the fault.

The purpose of this dissertation is to introduce the analytical solution for pressure-transient behavior for three novel reservoir models. First, we develop the analytical model of a multi-fracture horizontal well (MFHW) with pressure-dependent rock and fluid properties to study the impact of stress-dependent rock properties in composite unconventional systems. Second, we develop the analytical model for fluid-flow in a multi-well pad with three MFHWs in which wells can be interconnected through fracture hits. Lastly, we develop an analytical model of a compartmentalized reservoir with a segmenting fault in which fault permeability changes suddenly as a consequence of fault reactivation.

Governing equations for fluid-flow are based on Darcy's law. Pressure-dependent properties for the MFHW model are assumed to vary exponentially with local pressure-drawdown. Pressure-transient solution for each reservoir model is derived with the aid of advanced mathematical solution techniques, such as Laplace-Fourier transform and related numerical inversion, and iterative algorithms. Single-phase slightly compressible fluid-flow is considered for all reservoir models. Neither turbulence nor non-Darcy flow are considered in this work. Analytical solutions are presented as diagnostic plots and type curves.

Analytical solutions were successfully validated against numerical simulation data. The resulting diagnostic plots and type-curves for well-test interpretation are presented and discussed for each case study. Various sensitivity analyses were carried out to examine the impact of several parameters of interest on pressure-transient behavior.

In particular, we find that the effects of pressure-dependent fracture conductivity and stimulated reservoir properties, in conjunction, largely influence MFHW performance in stress-sensitivity formations. Likewise, we are able to detect and assess fracture hits by means of types-curves matching. Finally, we observe that fault reactivation can be detected on diagnostic plots as a sudden change in pressure-derivative response followed by a trend to attain late-time equilibrium.

Committee Chair

Zeidouni, Mehdi

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