Design Of Storage Fields With Minimum Temperature And Pressure Control At The Surface

Abstract

Abstract A stepwise procedure developed and presented last year (SPE 7495) for successive calculation of pressure and temperature gradients in gas wells has been applied to design of deep storage fields being developed in Northern Michigan. The calculation procedure has been cast in the form of an algorithm for quick and accurate implementation on a digital computer. The procedure has been improved with more accurate and procedure has been improved with more accurate and reliable subroutine packages giving enthalpies and further verified against more temperature/pressure data taken from Michigan Reefs in both Northern and Southern trend. In addition, an analytical procedure has been developed which gives the approximate temperature distribution from a generalized solution to energy balance expressed as a differential equation. A comparison of predicted vs. measured temperatures from actual field data, major design considerations directed to taking advantage of geothermal conditions around the well bore and unsteady state effects likely to occur are also entertained and presented in the paper. Introduction Respective technologies in underground storage and natural gas production are both supported by the same fundamental knowledge in geology, reservoir engineering, phase behavior and well mechanics. The differences recognized between storage and production usually relate to operational aspects and production usually relate to operational aspects and characteristics. The cyclic nature of injection/ withdrawal operations, high rates, use of pressures above discovery, constant monitoring, and inventory verification are among areas where these differences are observed. With increasing oil and gas prices and resultant emphasis on conservation recently, not only the need for more storage has been indicated, but reassessment of design procedures for more economic operation became desirable. Among the new ideas suggested were use of bottom hole chokes for control of pressure-flow conditions, and, where possible use of flow through casing or casing-tubing annulus which was shown to be more efficient in taking advantage of the geothermal temperature of the earth. With appropriate control of temperature and pressure, it was suggested that underground storage service pressure, it was suggested that underground storage service could be provided with a minimum of heating and pressure regulation at the surface. Design considerations related to temperature and pressure distributions through various casing-tubing-bottom hole choke combinations are also of continuing interest for application in geothermal wells, compressed air storage, production of oil and gas from arctic regions and underground storage of heat. The literature on temperature distributions include papers on unsteady state heat transfer into the well bore*, temperature distributions in water injection wells, temperature surveys in gas producing wells and analytical methods of calculating producing wells and analytical methods of calculating theoretical temperature distributions. More recently simplified methods based time dependent temperature effects became of interest for estimating pipe movements and thermal stresses. pipe movements and thermal stresses. In calculating temperature and pressure gradients up or down well bores last year, the authors presented a steady state procedure based on thermodynamic energy balance in well bores. That procedure has been improved through the use computer packages predicting the enthalpies more accurately and evaluated with data from gas storage reservoirs. In addition, it was found that a differential equation based on well bore energy balance would permit calculation of approximate but reasonably reliable temperature distributions in the well bore for conditions of flow with small pressure drop through casing or casing-tubing annulus. pressure drop through casing or casing-tubing annulus.