Unger Field, discovered in1955, has produced 8.6 million barrels of oil from a thinly (several ft) bedded, locally cherty dolomite containing vuggy and intercrystalline porosity. Today, the Siluro–Devonian Hunton Group reservoir is produced from 17 of the original 76 wells at an average rate of 2.6 BOPD. Water cut is high, indicative of a strong water drive. However, as wells are pumped hard oil production can increase, suggesting that bypassed oil remains. The Hunton Group subcrops and locally thins from 25 ft to 11 ft along a NW-trending anticline with a 30-foot structural closure. The original oil column is approximately 40 feet and the reservoir is overlain and underlain by thick shales. In an attempt to intercept bypassed oil an azimuthal gamma ray was used to “soft land” the well in the thin Hunton reservoir and geosteer the lateral for 1137 feet along the uppermost 5–10 feet of carbonate. The lateral parallels the east flank of the NW-trending anticline and encountered strong oil shows. Drill pipe-conveyed triple combo and microimaging logs were used to identify a 180-foot long interval of oil-saturated medium crystalline dolomite and minor fracturing. A slotted liner was used to isolate conductive fractures that trend E-NE, parallel to maximum horizontal compressive stress. Anisotropic drainage likely results from discrete fracture sets as inferred from the formation evaluation. Production and decline rates from this RPSEA-supported drilling project (07123-04) demonstrate that old fields can be revitalized using low-cost MWD tools to optimize lateral placement and thereby contact bypassed pay.
Topics covered include:
- Background on 57-year old Unger Field evaluating potential for bypassed production.
- Pre-spud analysis
- Regional and local structure and evaluating well trajectory.
- Stratigraphic framework of Hunton Dolomite reservoir mapping including flow unit characterization using old well logs.
- Well planning for soft land the well into top of the pay zone, set casing in pay and and drill out.
- Evaluation while drilling using azimuthal gamma ray, samples, and penetration rate.
- Post drill well shuttle logging with triple combo and imaging log to characterize fracture cluster and pay interval.
- Slotted liner completion to isolate the pay interval.
- Increased oil production from new well and nearby leases.
- Update on performance and options to further increase production.
Structure of the E-Symposium
Each e-symposium consists of one-hour live e-symposium, along with material for one full day of independent study. The live portion will be followed by a full day of independent study (not a live event). The one-hour live e-symposium can be accessed from any computer anywhere in the world using a high-speed internet connection. After the event is over, you will receive via email information about accessing the asynchronous segment (not live) which consists of your independent study materials, to be accessed and studied at any time. You will be able to email responses to the readings, along with your study question answers for CEU credit (if you sign up for the extended package).