This paper defines a method of increasing gas recovery and reserves by maximizing natural gas well deliverabilities. This method involves prevention of formation damage while drilling, prevention of formation damage while drilling, completing, and working over gas wells.
Included is the definition of the formation damage mechanisms attributable to drilling, completing, and working-over operations. Formation damage, the principle deterrent to maximum-productivity and recovery, involves the physicochemical relationships of fluid-systems with the formation. These relationships are herein defined and then specifically extended to include the effects on gas reservoirs. Of particular importance is a treatise on the effects on the relative permeability to gas from hydrocarbon invasion. permeability to gas from hydrocarbon invasion. This treatise includes a means to evaluate the vaporization-equilibrium constants of the invading complex hydrocarbons. These principles have then been used to develop an oil base fluid system that precludes formation damage and that has a filtrate that will be vaporized by produced gas to preclude any reduction in produced gas to preclude any reduction in relative permeability to gas.
Also presented are computed data, laboratory data, and field data from wells drilled and completed with various fluid systems. These data include core data, return permeability data, back-pressure tests, well productivity histories, and pressure buildup surveys. These data show substantially increased initial and ultimate income from gas wells when non-damaged completions are effected.
The current and forecasted natural gas shortages increase the importance of maximizing the initial productivity and ultimate recovery from gas wells. A frequent impediment to maximum well productivity and hydrocarbon recovery is formation damage that may occur during the drilling or completion operations.
