The Matzen Sand (16th TH) was discovered in 1949. To date, some 42.3 million m3 (266 million STB) oil and 3.75 billion m3(Vn) (140 billion scft) gas were produced which leads to a recovery factor of 48.5 %. Average water cut is 93.5 %. Mean porosity is 27 %. The oil has 25°API gravity. The sand is relatively homogeneous and exhibits a pay thickness between 1 m up to 70 m (3.3 ft to 230 ft). ‘Hard layers’ (tight streaks) reduce vertical permeability in certain areas.

1968 a peripheral water injection project was commenced. Discontinuous hard layers distributed throughout the reservoir affect water flooding. Sweep efficiency is related to these hard layers. Areas of unswept oil between these tight layers have been proved by reperforation of certain producing wells.

In 1996 natural gas injection started into the gas cap which caused a reduction of the oil production decline by 50 %.

Successful production history of the 16th TH results from proper reservoir management through 55 years of field life.

Keywords:
enhanced recovery, matzen sand, injection well, Upstream Oil & Gas, reservoir pressure, water cut, th TH, gas cap, gas injection, saturation
Subjects:
Well & Reservoir Surveillance and Monitoring, Reservoir Characterization, Fluid Characterization, Improved and Enhanced Recovery, Reservoir Simulation, Formation Evaluation & Management, Reserves Evaluation, Phase behavior and PVT measurements, Waterflooding, Gas-injection methods
Copyright 2006, Society of Petroleum Engineers
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