Examination of Unconventional Phenomena in Naturally Fracture Liquid-rich Gas Reservoirs: Single-block Compositional Model

Open Access
Author:
Al Ghamdi, Bander Nasser
Graduate Program:
Energy and Mineral Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 08, 2016
Committee Members:
  • Luis F Ayala H, Dissertation Advisor
  • Luis F Ayala H, Committee Chair
  • Turgay Ertekin, Committee Member
  • Eugene C Morgan, Committee Member
  • Mathieu Philippe Stienon, Committee Member
Keywords:
  • Liquid-Rich reservoirs
  • Diffusion
  • Naturally fractured systems
  • Capillary pressure
  • Unconventional reservoirs
  • Compositional
Abstract:
Liquid-rich gas reservoir development is highly dependent on the thermodynamic behavior of the fluids-in-place. During the depletion of liquid-rich gas reservoirs, the gas condenses as the pressure of the reservoir reduces below the hydrocarbon dew-point pressure, which introduces a liquid phase called retrograde condensate. In such conditions, the productivity experiences a reduction in recovery due to the appearance of condensate near the production channels, which in turn reduces the overall flow of hydrocarbons to the surface. A numerical compositional reservoir simulation was developed in-house to simulate the productivity of liquid-rich gas reservoirs in tight formations. The capability of the simulator proved to be successful after simulating a hypothetical case of a 2-D tight liquid-rich gas reservoir using the in-house simulator against commercial software CMG. The results of both simulators came into agreement with one producer well being put on production at a constrained bottom-hole flowing pressure of 1500 psia. The validation of the basic framework of the in-house simulator has provided the necessary confidence to extend the development of more complex models. The impact of capillary pressure on phase behavior was explored using an in-house generated coupled phase behavior model with a capillary pressure equation. The influence of capillary pressure was examined against different sets of composition combinations in different reservoir settings. The capillary forces' extents were highly dependent on composition combinations and pore radiuses. Mixtures with higher volatile concentrations showed the highest capillary forces. The enhancement in condensate propagation, resistance to gas flow, and impact on recovery were explored at 10 nm and 20 nm pore radiuses. The investigation suggested that interfacial tensions implied greater influence on the flow behavior in oil-dominated systems than in gas-dominated conditions. Evaluating the flow performance of unconventional phenomena in liquid-rich gas reservoirs was extended to include diffusion while activating capillary forces. The results showed higher domination of diffusion on reservoir performance which provided additional fluid recovery. Subsequently, the enhanced withdrawal of fluid dismissed the impact of capillary forces on gas flow and the impact of condensate blockage.