Identifier

etd-1106103-171111

Degree

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

Document Type

Dissertation

Abstract

Water inflow may cease production of gas wells, leaving a significant amount of gas in the reservoir. Conventional technologies of gas well dewatering remove water from inside the wellbore without controlling water at its source. This study addresses mechanisms of water inflow to gas wells and a new completion method to control it. In a vertical oil well, the water cone top is horizontal, but in a gas well, the gas/water interface tends to bend downwards. It could be economically possible to produce gas-water systems without water breakthrough. Non-Darcy flow effect (NDFE), vertical permeability, aquifer size, density of well perforation, and flow behind casing increase water coning/inflow to wells in homogeneous gas reservoirs with bottom water. NDFE is important in low-productivity gas reservoirs with low porosity and permeability. Also, NDFE should be considered in the reservoir (outside the well) to describe properly gas wells performance. A particular pattern of water rate in a gas well with leaking cement is revealed. The pattern might be used to diagnose the leak. The pattern explanation considers cement leak flow hydraulics. Water production depends on leak properties. Advanced methods at parametric experimental design and statistical analysis of regression, variance, with uncertainty (Monte Carlo) were used building economic model at gas wells with bottom water. Completion length optimization reveled that penetrating 80% of the gas zone gets the maximum net present value. The most promising Downhole Water Sink (DWS) installation in gas wells includes dual completion with an isolating packer and gravity gas-water separation at the bottom completion. In comparison to Downhole Gas/Water Separation wells, the DWS wells would recover about the same amount of gas but much sooner. The best DWS completion design should comprise a short top completion penetrating 20% - 40% of the gas zone, a long bottom completion penetrating the remaining gas zone, and vigorous pumping of water at the bottom completion. Being as close as practically possible the two completions are only separated by a packer. DWS should be installed early after water breakthrough.

Date

2003

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Andrew K. Wottanowicz

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