Horizontal wells present an effective method to maximize production potential and reduce development costs of some oil and gas fields. The ability to predict induced fracture direction with reasonable accuracy can allow the operator to drill in the direction considered most profitable.1 Ideally the well would have extended reach in the proper direction through a stable, fractured formation, would not require stimulation, and would not be subject to the production problems usually encountered in the life of a field. Since horizontal wells are drilled in a variety of formations, operators are experiencing the normal well problems and are finding stimulation and control methods useful for production improvement. This paper will examine problems associated with cementing of horizontal sections and the recent technology advancements that may be applied to help assure a competent annular hydraulic seal. Conventional cemented completions have not been used extensively in horizontal wells since some operators lack confidence in the technology that is available. Problems have been perceived in managing cuttings transport, pipe centralization, effective mud displacement, cement free-water control, and effective placement of a cement seal around the casing. These problems do exist and corrective techniques are complicated by highly deviated wellbores, but technology advances have been made to address horizontal conditions. Proper cementing may continue to provide an economical hydraulic seal for zonal or wellbore segment isolation so necessary to effective stimulation and work-over operations. The use of advanced technology often requires extensive pre-planning and includes the necessity to properly communicate the benefits to field operations personnel to assure the proper implementation of new or different techniques or materials. Little good will come from the best ideas without proper follow-through during application.

SPE Members Abstract Extended-life polymer gel plugs have met rigorous requirements as a sealant for restoring a barrier in the tubing annulus when tubing-annulus leakage has occurred. These requirements include urgency to restore annulus integrity dynamic placement in unbalanced well conditions, and ease of removal without milling the tubing. Very attractive economic benefits have resulted. Introduction Casing deformation resulting from reservoir compaction has caused 45 well workovers, starting in 1981, in three of the Greater Ekofisk Area fields. The Ekofisk, Eldfisk, and West Ekofisk fields are located in the southern portion of the Norwegian sector of the North Sea (Fig. 1). Compaction of up to 30 ft has deformed casing both in the chalk reservoirs and in the overburden formations. Deformation in the overburden leads to tubing damage and leakage causing the well to be plugged and scheduled for a sidetrack workover when a rig is available. This paper describes experiences with extended life polymer gel (ELPG) plugs to seal leaking tubing annuli, thus allowing the wells to continue to produce until workover is practical. Gel characteristics determined by laboratory testing are presented, the placement techniques in wells are described, and field experience is given with regard to plug life and removal for well workovers. The present well failure rate of five to eight wells per year along with the shut-in time of 6 months or more before a rig is available has significant economic consequences. The demanding requirements for an annulus sealing method include urgency to restore the annulus barrier, dynamic placement in unbalanced well conditions, effective sealing of the annular area, and obtaining a plug which can be easily removed without milling. Gel plugs have proven to be a reliable and cost effective sealing system for this application. CASING DEFORMATION Casing deformation caused by reservoir compaction (Fig. 2) is the dominant mechanism for well failure at Greater Ekofisk. As the originally overpressured, high-porosity chalk formations are being depleted, reservoir compaction results. P. 201^