ABSTRACT: Entrapment control and play fairways in interorogenic setting - An example from Assam petroliferous province of India

Jokhan, Ram , Oil & Natural Gas Corporation Ltd, Nazira, Assam, India

While the structural style in the classical thrust-fold belt is well documented, the interorogenic settings, being more complex, have not been investigated in detail. It is, however, easy to comprehend that mutually opposing stresses and direction of tectonic transport operating on a common foreland could result in frequent disruptions of tectonic fabric. The latter has serious implication on the petroleum system including disruption and re-migration of pools. It is, therefore, surmised that numerous small/marginal fields strewn all along the interorogenic basin are characteristic of complex tectonic fabric of interorogenic settings as against the giants and super giants of the mildly deformed classical foredeep/foreland settings.

This paper discusses the structural style of the interorogenic foreland and proposes an exploration model for play fairways in such settings with examples from Assam petroliferous province of the Indian subcontinent, one of the oldest known petroleum provinces of the world. The isopach analysis suggests that Arakan-Yoma system largely controlled the basin's polarity till the end of Girujan deposition (6 ma). The large wavelength fault propagated folds and piggy-back structures thus formed, were subsequently segmented by Himalayan orogenic front as it advanced south-eastwards. The structural style and dispersed habitat of hydrocarbon with small individual field - pool sizes of Assam petroleum province compare very well with similar settings in Potwar region of Pakistan and south-east Turkey. Thus the interorogenic settings represent a distinctive class within the foredeep-foreland category with its unique play fairways.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia