Affiliation:
1. Chevron Energy Technology Company
Abstract
Summary
High-pressure, low-permeability reservoirs have been encountered in various parts of the world within the past few years. Commercial development of these reservoirs may require operating wells with high drawdown pressures, possibly in excess of 6,000 psi. The effects of drawdown pressures in this range are increases in nearwellbore temperatures because of Joule-Thomson expansion of the reservoir fluids and significant reductions in oil viscosity. The effects of high drawdown pressures are evaluated with a transient, singlephase thermal simulator in which the oil viscosity is modeled as both temperature and pressure dependent and Joule-Thomson expansion and viscous dissipation effects are considered. Results indicate near-wellbore temperature increases of 4 to 28°F for drawdowns between 2,000 to 10,000 psi because of Joule-Thomson expansion of the reservoir oil and connate water. Furthermore, if oil viscosity is not modeled as pressure dependent, skin values from well tests and productivity indices will be underpredicted. Temperature profiles within the formation are presented for a range of rates and drawdowns. Technical rationale is also presented to explain the transient heating or cooling phenomena that occur immediately after a rate change. Synthetic well tests are generated to illustrate the effect of high drawdown on well test interpretation. These tests show a region of improved mobility in the near-wellbore region because of the reduction in the oil viscosity.
Publisher
Society of Petroleum Engineers (SPE)
Subject
Geotechnical Engineering and Engineering Geology,Energy Engineering and Power Technology
Cited by
34 articles.
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