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Halpern, Henry I.1, Peter J. Jones1, Salman M. Al-Qathami1, Khalid R. Al-Malki1
(1) Saudi Aramco, Dhahran, Saudi Arabia

ABSTRACT: Applications of Pyrolysis to Optimize Oil Field Development in Saudi Arabia: Part 1 - Prior to Drilling Phase

Planning the development of the Arab-C Reservoir at Qatif Field has involved a variety of complex issues that are critical to optimizing operations and performance objectives. One of the major complications to field development is the existence of a substantial tar mat on the flanks of the field. The position of this tar mat greatly limits the options for placement of horizontal power water injectors (HPWIs) at the periphery of the field.
The tar mat varies from wholly tar-occluded with no associated fluid moveability, to partially occluded resulting in either a marked or limited reduction in reservoir performance. Typical tools to assess tar occlusion are visual examination of cores and moveable hydrocarbon plots from electric logs. Visual estimations tend to overestimate the quantity of tar present, and, while moveable hydrocarbon plots can be very effective in identifying completely tar occluded pore space, partially tar occluded reservoir that is within the oil-water transition zone is extremely difficult to assess with historical logging tools.
Several powerful pyrolytic methods have been developed in recent years at Saudi Aramco. These include the Pyrolytic Oil Productivity Index (POPI), Apparent Water Saturation (ASw), and the Compositional Modeling Method. The data derived from these techniques provide a more definitive assessment of the extent of tar than electric log data and have proved to be a cost-effective and reliable tool that is critical for mapping tar occurrence and planning effective placement of HPWIs.
This paper will cover use of pyrolysis to assess changes in reservoir facies, the expression of oil-water transition zones, the occurrence of tar, the differentiation and quantification of heavy oil, tar, and pyrobitumen within the reservoir, and the integration of this data with other sources to target the placement of HPWIs.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.