Play Conditions of Palaeozoic in Saudi Arabia Basin

Zuo, Guoping; Fan, Guozhang; Lv, Fuliang
Department of Offshore Petroleum Exploration, Petrochina Hangzhou Institute of Geology, Hangzhou, China.

This paper demonstrated the play conditions of palaeozoic in Saudi Arabia Basin by means of the study of source rocks, reservoir, seal, traps and migration.

Multiple source rocks developed in Saudi Arabia Basin. The dominated one developed in the Qalibah formation of Silurian. Qusaiba shale in Qalibah formation features high abundance, fine type, high thermal evolution and wide distribution. Organic matter mainly relies on type 2 kerogen. The windows of oil generation, condensate gas generation and dry gas are 230Ma, 140Ma and 90Ma, separately. These source rocks are the major factor of hydrocarbon enrichment.

Good quality of reservoirs distribute widely in Saudi Arabia Basin. They represent thick pay, high porosity and high permeability. They appear good lateral connectivity due to wide sediment and weak tectonic movement, but undergo different tectonic evolution, thus indicate obvious longitudinal heterogeneity. Reservoirs in Palaeozoic are dominated by sandstone of Jauf formation in Devonian and Unayzah formation in Permian. Due to the influence of cementation, quality of this kind reservoir changes rapidly in the lateral and vertical direction, therefore, it appears great heterogeneity.

Several seals contained in Palaeozoic petroleum system. The tight carbonate rocks overlay Unayzah formation act as the primary regional seal, which distributed widely, in addition, the internal mudstones also can be considered to be effect seals. D3B formation appears the dominated seal of Jauf formation, the thickness of which is thin, but developed in large scale. It shows as a marker formation in Saudi Arabia Basin.

The evolution of Arabia plate represents a steady continent block in the long geological history period. Most of the field are dominated by anticline structures, which features small angle of dip, thus, they are easy to form large scale traps. The basement map indicates that faults developed along NS direction, which is coincide with the distribution of grabens and horsts. Four periods are contained in the formation of traps in Palaeozoic petroleum system.

Fault is undeveloped in Saudi Arabia Basin except few regional fault, thus, layers show poor connectivity in the vertical direction. Gas migration focused on the unconformity, fracture and expansion.

Generally speaking, Paloeozoic petroleum system in Saudi Arabia Basin features reservoirs overlay source rocks, traps formed in the early period and gas filled in the later period.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012