Abstract

An alternative system to conventional HEC (hydroxyethylcellulose) and particulate fluid loss materials has been developed for fluid loss control in high permeability Gulf of Mexico Flexure trend completions. In offshore operations, the problem of controlling fluid loss to the formation is critical in achieving successful gravel pack completions. The problem is magnified in this environment because of the use of expensive high density brine, lost rig time, and increased standards for well control and safety. A newly developed fluid loss system which consists of a crosslinkable, derivatized HEC incorporating a branched functional group on an HEC backbone has been evolving in the industry. The functional group provides a nonionic reaction site which allows the polymer to be crosslinked at a low pH, and broken in a controlled manner using a newly pH, and broken in a controlled manner using a newly developed breaker.

Other fluid loss control systems used in Flexure trend completions exhibit specific problems which can be attributed to (1) physical properties of the particular material, and (2) the method of application. For instance, in many high permeability wells, noncrosslinkable HEC pills have permeability wells, noncrosslinkable HEC pills have proven inadequate for controlling fluid loss to an proven inadequate for controlling fluid loss to an acceptable level, and in some cases have allowed significant invasion of HEC, thus potentially resulting in permeability impairment. Particulate fluid loss materials present other problems in that they can be difficult to remove from perforations.

Laboratory and field tests demonstrate efficient fluid loss control and potential for reduced formation damage with this new crosslinkable HEC (CLHEC). Internally broken crosslinked gel has shown more favorable return permeability in core tests than regular HEC polymer commonly used in the industry. The CLHEC system deposits a thin, crosslinked polymer filter cake which helps prevent fluid loss, but which can be removed by means of an internal breaker, an acid wash, or both. Subject paper presents laboratory and field data illustrating paper presents laboratory and field data illustrating properties of the new fluid loss control system in properties of the new fluid loss control system in high density brine applications.

Introduction

Fluid loss control in offshore gravel pack completions has become an important subject in recent years with the increased awareness of the adverse effects inadequate fluid loss control and some fluid loss materials can have on gravel placement and well productivity. productivity. Controlling fluid loss rate before, during, and following gravel pack placement is essential in Flexure trend completions to prevent (1) formation damage, and (2) loss of expensive high density brines used to provide well control in high permeability unconsolidated sandstones. This situation is compounded by the relatively high overbalance pressures required to control high pressure pressures required to control high pressure formations. Excessive fluid losses in this environment can lead to unsafe well conditions.

Conventional fluid loss control systems applicable to gravel pack completions can be grouped into two general categories: particulate systems and gel systems. Particulate systems may include oil, acid, or water-soluble, properly sized particles. Gel systems can include a number of high viscosity gel pills.

A crosslinkable HEC fluid loss control system has recently been applied to Gulf of Mexico Flexure trend completions as an alternative to conventional methods of fluid loss control which is especially applicable, but not limited to these high productivity Gulf of Mexico completions. productivity Gulf of Mexico completions. P. 465

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