Integrated Reservoir Characterization of a Thinly Bedded Carbonate Reservoir to Improve Waterflooding in Horizontal Wells in the D Field, Oman

Fangming Li and Guoliang Zhao
CNPC International Research Center, Beijing, China

The D Field, discovered in 1986, is located between the Eastern Platform and Bab Basin, Oman. Reservoir rocks are dominated by Cretaceous bioclastic packstones and wackstones, which were buried at depths ranging from 1,500 m to 1,700 m. As of end-2006, 119 wells had been drilled, 88 of which are horizontal wells. Waterflooding in the field initiated in 2001; however, no significant production achieved until 2005 after an integrated reservoir characterization is applied to improve waterflooding in horizontal wells.

Under the framework of high-resolution sequence stratigraphy, the distribution of thinly bedded carbonate reservoirs has been predicted by applying seismic attribute and well logging constrained seismic inversion methods. These predicted reservoirs have been confirmed by outposts, with an initial oil production rate as high as 800 bbl/d in one outpost. As a result, significant reserves have been added in the past two years.

In order to improve waterflooding in horizontal wells, a three-step modeling strategy has been employed, including 1) geological conceptual model, 2) facies model, and 3) petrophysical model. Combined deterministic and stochastic geological modeling has been applied in step 2 and 3. As a result, a detailed reservoir geological model was established, which has been used as a guidance in the design of horizontal wells and waterflooding. After two years waterflooding study, daily oil production rate increased about 500 bbl in horizontal wells.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas