Horizontal Wells in a Steamdrive in the Midway Sunset Field

Abstract

SUMMARY Three horizontal wells have been drilled in a low pressure, mature steam drive at the D&E Unit of the Midway Sunset Field, Kern County, California. Simulation studies indicate that horizontal wells in thermal projects can increase recovery efficiency due to better a real sweep, accelerate production which improves the oil-steam ratio (OSR), shorten project life, and increase project profitability. The D&E Unit was selected as a test site for horizontal wells because gravel packs were not required for sand control. Low reservoir pressures and moderately sorted, sub-rounded sands contribute to the success of slotted liner completions. The reservoir is composed of well sorted, thick turbidite sands which dip at about 45°. The first two wells were drilled at an oblique angle to dip with approximately 400' laterals. The third well was drilled on strike with slightly more than a 700' lateral. Radius of curvature is approximately 40'. The three wells were drilled as short radius horizontal wells due to well and lease spacing constraints. The short radius design allows the rod pump to be placed in the vertical section of the hde with minimal draw down sacrifice. The lowest point of the laterals is 10' above the oil-water contact. All wells are completed with dotted liners. The three horizontal wells cost 2-3 times more than vertical wells. Oil production rates increased 2-3 times more than vertical wells in the two wells with 400' laterals. The third well with a 700' lateral is more prolific with 6 times the production rate of a vertical well. At this time, the wells are too immature to accurately predict ultimate recovery. This paper will discuss the drilling and completion design of the wells, steam soak data, temperature logs in the horizontal section and current production results. EXPECTED BENEFITS Simulation work has shown that horizontal wells in thermal drives accelerate production and increase recovery efficiency by improving a real sweep1,3,4,5 Increased production rates are a result of longer completed intervals and the additional draw down derived from placing the wells at the base of pay. In 1986, Huang, et al1 indicated that project improvement derived from horizontal well development could be dramatic; simulation results predicted a 250 percent increase in initial production rate. The best ease in the simulation reduced project life from 15 to 7 years. Other potential benefits include producing reserves between the oil-water contact and existing completions. Many existing wells were completed shallow to avoid penetrating the transition zone. Horizontal wells may be the most effective way to exploit this wedge of undeveloped reserves. Vertical wells frequently suffer from production problems Stemming from steam entry into the wellbore. Steam entry may cause sanding, liner damage, and high casing pressures. Horizontal wells would not "steam out" until the steam drive is very mature, therefore remedial work maybe significantly reduced.