The Fractured Basement in Block 10 of Yemen: A Successfully Appraised Nonconventional Play and Challenges for Future Development

de Clarens, Philippe ¹; Langevin, Nicolas ¹; Duneau, Jean Pierre ²; Gauthier, Bertrand D.M. ³
(1) TOTAL, Paris La Défense, France. (2) TOTAL E&P Yemen, Sanaa, Yemen. (3) TOTAL, Pau, France.

In 1992, oil was found in basement in a Jurassic to Lower Cretaceous rift in Yemen, on a license operated by TOTAL. The Kharir field is still today, after a number of other discoveries in the basement, the largest and most productive field at this nonconventional play in Yemen. Being the secondary objective in the discovery well and despite a production test evidencing producible oil, the Basement was first abandoned to develop the much better producing directly overlying prolific Cretaceous play.

Appraisal of the Basement play in KHARIR was pursued by deepening development wells targeting the overlying conventional Cretaceous play. In a short period, several successful production tests were carried out in the Basement sections with production rates up to 7000 bopd.

After initial mechanical difficulties to obtain successful penetration in the Basement, part of the challenge remains the characterisation and the estimation of the oil in place of this non-conventional reservoir. With a seismic of medium quality, the assessment of fault schemes of deep horizons and the prediction of sweet spots remains difficult. Adding to these uncertainties are the consequence of the choice of the pressure maintenance mechanism and incompatibility of produced effluent with existing production facilities. The combination of these elements has led Total to implement a phased development approach including early production facilities with a gradual increasing well count while the overall development plan for the Basement is being developed.

With the successful development of KHARIR, the fractured Basement reservoir has become a key exploration objective in and around the Jurassic to Lower Cretaceous graben in Yemen as well as in other prospective areas. However, basement exploration and production require addressing specific challenges at each phase of prospect/field/reservoir life: 1) Define what are the geological settings required for a basement rock to be a successful play; 2) drilling and evaluate the objective; 3) estimates porosity and permeability figures in order to estimate in places and deliverability; 4) produce economically and predict reservoir behaviour to depletion and injection.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.