Innovative Workflows for Mitigating the Horizontal Well Placement Challenges Associated With Deep Unconventional Reservoirs

Abstract

Kuwait Oil company is currently engaged in an early phase of appraisal of the deep tight fractured carbonate reservoirs and resource plays of Oxfordian – Callovian age (over 14000ft depth, HPHT) in the northern part of Kuwait. The primary driver for successful appraisal of such unconventional reservoirs is optimal wellbore design (horizontal well) maximizing reservoir contact which intersects open fractures or facilitates effective hydraulic fracturing. The key factors that determine the success in achieving the objectives of these horizontal wells are well selection, well placement and well testing and completion. The well design and placement of these horizontal wells is severely constrained by the very highly overpressured (upto 21 ppg mud weight equivalent) evaporite section (Salt+Anhydrite) overlying the target unconventional reservoirs. Although, the individual thickness of the reservoir units range from 40′-50′, for well placement / geo-steering purposes the sweet spot within these units is of the order of 5′-10′. Due to resolution limitation of the available 3D seismic data, predicting local dip changes of the order 1°-2° and very minor subseismic faults at the depth range of 14000′-15000′ is fraught with higher uncertainty. To mitigate the well placement challenges and maximize success, utilising innovative workflows many iterations / updating of the initial fine scale static model (which is constrained by the offset well data and 3D seismic data) are carried out and different potential scenarios (for changes in dip and observed apparent thickness changes as a result of the combination of bed dip and inclination of the well) are prepared dynamically in conjunction with the well placement team to assist in real time geosteering of the well. Taking into consideration the lessons learnt from the two horizontal wells drilled recently, the above novel approach has resulted in 100% placement of 2000′ drain hole in the third well (final TD: approx.. 19000′ MD) targeting the deep unconventional reservoir in northern part of Kuwait.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015