Abstract
Development of marginal fields offers unique challenges during drilling, completion, stimulation, and production. The underlying objective should be to maximize the value of the field over its productive lifetime. Every phase of the well construction needs to be fully evaluated for subsequent impact on the safety and economics of producing oil and gas from the field. Log evaluation of formation type, thickness, and characteristics may determine the final completion plan, although lack of natural barriers from close water contact may be of major concern when a large stimulation program is required. Specialized low-density cementing systems may be necessary for maintaining satisfactory equivalent circulating density (ECD) for coverage across weak formations. These low-density systems can be prepared either by an engineered foaming operation or by the use of specialized additives blended with cement to lower the density, but production quality properties should be maintained. Consideration should also be given to the final cement sheath properties, which can provide isolation for the "life of well" following cyclic pressure loading from stimulation, testing, and flowing phases.
This paper addresses the advantages and disadvantages of the historical approach to constructing and producing horizontals. Completion processes and procedures with emphasis on cementation designs and best practices for horizontal casing are presented with major focus on resulting production rates. These case histories will cover both cemented and uncemented producing wells. Also included will be new methods for predicting cement failure modes as a result of cyclic pressure loading from stimulation jobs. Recent design procedures and ensuing effect for maximum value of the producing asset for life of the field will be compared with historical procedures.
