Using Fault Seal to Determine Dependencies between Adjacent Traps and Calculate Trap Risk

Brown, John P.¹; Mustahim, Suriani ²; Sathasivam, Sundaresan ²; Tedjoyono, Bambang ²; Razikin, En M.^2
1 XTG, PETRONAS Carigali, Kuala Lumpur, Malaysia.
² Exploration Devision, PETRONAS Carigali, Kuala Lumpur, Malaysia.

During the exploration and development of faulted traps the ability of faults to either compartmentalize a trap (seal) or to act as intra-reservoir connections (leak) has a fundamental effect on how traps are risked, how associated oil or gas volumes are calculated and how development wells are planned.

The geological uncertainty associated with fault compartmentalization is compounded if multiple faulted traps exist in close proximity or on the same structure. In this scenario it is vital to assess whether or not the traps are dependant or independent and if there is a dependant relationship, how will these dependencies affect trap risk and reserves?

In the workflow presented here fault plane profiles (or Allan diagrams) are used to screen trap bounding faults and determine the overall fault seal / fault leak potential and to estimate the position and elevation of potential communication points between stacked reservoirs that are separated by a fault. Fault seal and leak point data are then combined with structural spill points and migration directions to assess dependencies between adjacent fault traps.

Two studies from SE Asia will be used to illustrate the workflow. The first study shows how multiple dependencies between adjacent fault traps effect trap risk and reserve estimates. The second illustrates how leaking faults can create independent traps, despite being located on the same structural closure.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009