Porosity System Architecture and Their Impact from Oil Production - a Case Study of Aries Oil Field, Kazakhstan
In this paper, reservoir heterogeneity problem was tackled in the pay formation of Aries Oil Field, a set of drape structural oil accumulations discovered in the south part of Tulgai Basin, Kazakhstan. The evaluation target, Cretaceous Klnclar Formation, was mainly estuary siliciclastic sandstone with clay lamination deposited in a deltaic system. Production rate of this reservoir suffered significant decline due to insufficient understanding of the reservoir in detail. Pore type definition and pore system architecture analysis were discussed in this paper, accompanied with necessary petrological and diagenesis examination. New injection plans were executed based on this study and show promising results.
The local multi-current sedimentary environment predestined the intricate nature of the reservoir and non-reservoir combinations. Various types of pores could be found in these sandstone intervals, but conventional inter-granular and dissolution pores played the large part, leaving a small amount of pore volume to the most complex pore types derived from complicated subsurface physical-chemical processes. The main oil bearing pore system comprised of large pore spaces interconnected with coarse throat, but the high carbonate cement content and their irregular distribution could deadly impair the fluid conductivity. The low quality beds with fine grains and heavy matrix intertwined with the main reservoir had to be dealt with as well. Clay contents were defined by means of Scanning Electron Microscopy, and their impact on water injection was evaluated.
New water injection and gas injection program was carried out after this study and some typical improvement has been observed: slowing down of oil rate decline in one month, rising of oil rate after four months. But there seemed still a few wells untouched, i.e. they did not show a better productivity after the modification of producing pattern. Some more complicated factors had to be found through more thorough analysis. This paper is helpful to those interested in IOR project.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009