Parametric Pulsing A New Approach to Increased Gas Field Deliverability
Authors: Tek M.R. , Hedges E.B. , Gould T.L. 
Published: December 2007

Considering the current tight supply of gas and the high cost of equipment, increased deliverability in production or increased cyclic capacity in storage have become particularly desirable. Here is a possible, feasible, and operable concept for achieving those ends.

Introduction

Many engineering operations utilizing rate processes indicate that unsteady-state rates are almost invariably higher than the steady-state values to which the particular system settles down eventually. For heat particular system settles down eventually. For heat transfer, mass transfer, and reaction kinetics, examples may be cited in which transient rates are greater than their steady-state values. The same is true in diffusional flow of natural gas through porous media. That is wily gas wells during early times of their production perform at rates higher than their steady-state rates. When a gas well is first turned on to flow at a given choke setting, the porous matrix is subject to maximum driving force; i.e., pressure drop between the wellbore and the adjacent porous medium. Anyone involved in field testing of gas wells observes high metered rates at the beginning of the allow period before the drainage radius propagates toward the boundaries of the reservoir and conditions begin to settle down to steady state. The length of time for the transient condition to decay into steady state depends upon many factors such as porosity, permeability, pressure level, and geometry. In highly permeability, pressure level, and geometry. In highly permeable reservoirs it is only a matter of minutes permeable reservoirs it is only a matter of minutes before steady state is established. By contrast, in tight and heterogeneous formations, the transients may persist for weeks, sometimes even months. By not persist for weeks, sometimes even months. By not allowing the system to linger on to steady state, high instantaneous rates can be maintained and high production can be realized. This approach has been tried production can be realized. This approach has been tried in many industries, and continues to be tried, but very, little has been published on the subject.

Many cyclic processes currently in research or pilot trial stage in heat transfer, reaction kinetics, and mass transfer result from such attempts to maintain the system in a "succession of unsteady states." The steam-soaking and huff-and-puff methods of thermal oil recovery are perhaps the first operations in the oil industry for which engineers are compelled to seek reasonable economic rates through cyclic operations.

In the gas industry, increased deliverability in production or increased cyclic capacity in storage, production or increased cyclic capacity in storage, becomes particular desirable in light of economics related to current tight supply and high costs. Rather than adding to the existing plant (more wells, more compression, higher-pressure piping, more well stimulation), the goal of increased seasonal or cumulative deliverability may be achieved through optimized engineering operations.

Concept and Theory of Parametric Pulsing

"Parametric Pulsing" is a term coined to describe a concept of gas production or injection whereby high rates and consequently high cumulative deliveries would be achieved through an optimized "pulsed" mode of operation rather than through continuous flow. The concept is best applied to certain types of reservoirs. In others, operations are only marginally enhanced. In still others, it may well be that the pulsed mode produces less than the continuous mode.

JPT

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