Effect of Preheating on Kern River Field Steam Drive

Abstract

Summary The productive formation in the Kern River field is a sequence of sands designated as the Kern River series. These fine to very coarse sands, each averaging 60 ft (18.3 m) in thickness, are separated by silt and clay interbeds. They are steam-displaced sequentially from the bottom up, one zone at a time. Since steam drive became a viable recovery technique in the early 1960's, all Kern River field steamdrive design and planning was based on the use of a reservoir temperature of 85 to 90°F (29 to 32°C). It was recognized that zones immediately above a previously displaced interval eventually will become heated by the zone below through heat conduction. To a lesser degree, this also occurs in zones below the active drive. With sufficient preheating, very thin sands, previously calculated to be uneconomical and scheduled to be deferred in favor of thicker sands, have proved very productive. The preheating of thicker sands also has resulted in significantly higher production rates than the non heated equivalent sands. This paper discusses the numerical modeling work completed to evaluate the effects of preheating. Field results, including temperature surveys and production data, also are presented to substantiate the theoretical work and prove that preheating effects are an important consideration in a steamdrive operation. Introduction The Kern River field is a large, shallow, heavy-oil deposit located 5 miles (8 km) northeast of Bakersfield, CA. The reservoir is a sequence of up to seven sands designated as the Kern River series. These sands are separated by silt and clay interbeds. Both reservoir and fluid characteristics are very favorable for steamflood methods. The unconsolidated sands have high permeabilities of 1 to 5 darcies and porosities of 28 to 33 %. The average oil viscosity and reservoir temperature are 4,000 cp (4 Pa · s) and 85°F (29°C).