A New Method of Sand Control: The Process and its First Field Implementation

Abstract

Abstract A new method of sand control 1,2, which was earlier developed and tested in the laboratory, has been implemented and evaluated in the field. The method is based on a low-temperature oxidation process where a hydrocarbon fluid wetting the sand grains is oxidized resulting in a coke-like solid substance that cements and consolidates the sand grains. Laboratory development work involved first a series of experiments on small loose-sand packs with the purpose of investigating the effects of control parameters on the quality of sand consolidation and determining the optimum process conditions. Employing the optimum conditions, the process was then tested on a full-scale wellbore model resembling specific actual field conditions. The results of this development work proved that the new method is viable and is potentially superior to existing sand control methods. The new process was then designed for field-scale applications and was implemented on a well with potential sand production problem. The well was flowing initially at low rates between 200 to 400 bpd and was cutting little sand. Other wells in the field producing at higher rates were experiencing major sand production problems. Following treatment of the well with the new process, the well was produced with ESP at a rate of 4000 bpd without sand production. Close monitoring of the well for more than three months showed no significant rise in sand production. Introduction Sand production, associated with the production of oil, gas and water, is a very serious problem that is encountered in many fields around the world. Sand production may result in potentially hazardous situations when sand is produced at high rates causing quick erosion and failure of subsurface and surface well-control equipment. Less serious, but very costly, situations may be experienced when sand production necessitates frequent sand wash-out operations, cleaning of surface facilities, and replacement of subsurface and surface facilities. Sand production occurs when the flow-induced drag forces exceed the restraining forces that hold the sand grains together. Sand will be produced from any sandstone formation when a certain fluid flow rate through the formation is reached. This rate, known as the critical rate, depends on the strength of the formation and the properties of the flowing fluid. The pressure drop across the formation associated with the critical rate is known as the critical drawdown. The critical rate (or drawdown) is usually low for unconsolidated or weakly consolidated sand formations; consequently, production of hydrocarbons or water from such formations is normally associated with sand production. A few methods exist for sand control; these are classified as completion and production practices and mechanical and chemical methods. Proper completion practices are always recommended to minimize near-wellbore formation damage and reduce the pressure drop across the formation and perforations. Sand production can be eliminated by producing at rates below the critical rate for a given formation. In most cases, however, the critical production rates are either not economical or much lower than the production potential of the well. Sand production may be minimized or stopped by mechanical means such as the placement of a screen or a slotted liner opposite the producing formation. Screens and liners, however, may only be used as a temporary solution to the problem as they erode very quickly and require frequent replacement. Gravel packing is the oldest and most commonly used mechanical means for sand control. In addition to its high cost, gravel packing normally restricts the productivity of the well as it reduces the wellbore diameter of cased wells, adds a positive skin and may require frequent repairs. Further, gravel packing cannot be used for slim-hole and tubingless completions. Chemical (plastic) consolidation of the formation around the wellbore is another means of sand control that has been in use for many years. However, plastic consolidation methods are very expensive, result in significant loss of permeability, and have numerous technical limitations.