AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Carbonate Ramp Nummulite Limestone Reservoir Integrated Research in Pelagian Basin, Libya
(1) Research Institute of Petroleum Exploration&Development-Northwest(NWGI),PetroChina, Lanzhou, China.
As a Mesozoic to Cenozoic superposition basin, Pelagian basin consists of Libya and Tunis two countries, and was one of the most important petroliferous basins in North Africa. The discovered reserves in sea area was olny more than 3% of total discovered in Libya, which showed its low degree of exploration and huge residual resource potential. The study area included three structural zones, which was Jarrafa arch, Zohra graben, and Sabratah slope. The main reservoir was nummulite limestone in Metlaoui group, Lower Eocene, which was bioclast limestone bar and beach facies in carbonate ramp. Applying the theory of high resolution sequence stratigraphy, sedimetology, and petroleum geology, using well logging, diplog, and seismic data, the sequence stratigraphy classification and correlation of key wells were confirmed, and the sequence framework was established. Four cycles were divided in intended interval, which represented different microfacies.Palaeostructure, palaeoenvironment, the location in ramp, sealevel and wave controlled the main reservoir development by sedimentary controlling factor and distribution rule analysis. Sedimentary system distribution and evolvement model were build, which explained the evolutionary process and the cause of reservoir lateral variation and the loss drilling well. Applying the geophysical theory, using the reservoir prediction technique of forward modeling, seismic attributes, impedance inversion and hydrocarbon detection synthetically and combining with sedimentary system, the favorable reservoir distribution was predicted in study area. The nummulite limestone boundary can be enlarged northward compared with the former recognition. The reservoir developed on the top of palaeostructural high was denuded partly, but the periclinal zone should preserve nummulite limestone, which can form traps even hydrocarbon reservoirs under certain condition. All the above conclusions can provide some foundation for next exploration.