Marin Čikeš

Sand Control in Well Construction and Operation

Produced sand causes a lot of problems. From those reasons sand production must be monitored and kept within acceptable limits. Sand control problems in wells result from improper completion techniques or changes in reservoir properties. The idea is to provide support to the formation to prevent movement under stresses resulting from fluid flow from reservoir to well bore. That means that sand control often results with reduced well production. Control of sand production is achieved by: reducing drag forces (the cheapest and most effective method), mechanical sand bridging (screens, gravel packs) and increasing of formation strength (chemical consolidation). For open hole completions or with un-cemented slotted liners/screens sand failure will occur and must be predicted. Frac-and-pack combines the stimulation advantages of hydraulic fracturing with the most effective techniques available for sand control in poorly consolidated, high-permeability formations

Sand Control Methods

The main purpose of any sand control method is to hold load bearing solids in the place. It is therefore necessary to determine what is in fact produced. Some fines are always produced, and that can be beneficial because that helps in cleaning pore space. The other (solids between 50 and 75 percentile ranges) that are real load bearing solids can be control through reduction of drag forces, by bridging sand mechanically or by increasing formation strength. That means some kind of production rate control, selective or oriented perforating, fracturing and gravel packing, use of screens and chemical consolidation.

Frac-and-Pack Completion

A relatively short, highly conductive fracture created in a reservoir of moderate to high permeability will breach near-wellbore damage, reduce the drawdown and near-wellbore flow velocity and stresses, and increase effective wellbore radius. Fracturing treatments of this type have two stages: fracture created, terminated by tip-screenout, and fracture inflation and packing. Such a two-stage treatment is the basis of a number of well-completion methods, collectively known as frac-and-pack. This technique has been successfully applied, with a range of fracture sizes, to stimulate wells in various reservoirs worldwide.

Perforating for Sand Control

To assure the success of sand control job in cased and cemented wellbore it is essential to proper design and execute the perforating program. The definition of adequate number of perforations with sufficient depth of penetration (length) will allow production with desired production rate.

Formation Sampling and Sand Analysis

The starting point for any kind of sand control with respect to geomechanical approach is proper sampling and sand screen analysis. Use of bailed or produced sand samples leads to mistakes and problems and is the poorest kind of data that can be used in designing sand control. The representative samples are obtained by coring the whole length of the interval with adequate coring equipment. Particle size distribution is then determined through sieve and laser particle size (LPS) analysis.

Treating Fluid Selection

The major types of treating fluids that are in use in sand control are conventional linear gels, borate-crosslinked fluids, organometallic-crosslinked fluids, and aluminum phosphate-ester oil gels. The general behavior of these fluid systems is described. Fluid loss properties, breaking systems, and resulting formation damage are discussed and recommendations for treating fluid selection in sand control are offered.

Downhole and Surface Equipment

Completion as such is meant to be a link between drilling the borehole and the production phase. Without completing the well, hydrocarbons are not able to flow up hole under control. As a phrase, completion involves all the wellbore tools, accessories or tool assemblies involved in any wellbore operation. On the other hand, without proper surface equipment, which is one of the key factors for successful sand control operation execution, it is not possible to treat the fluid on the surface and pump it downhole.

WELL COMPLETION OPTIMIZATION FOR UNDERGROUND GAS STORAGE

Information systems of all kinds are increasingly being applied to improve the management and control of goods movement. Commonly expected benefits include less inventory in the supply chain and enhanced levels of customer service. One important example of a transport information system is track and trace, in which the movements of a particular consignment can be monitored as it passes through the transport network. In many cases the application of track and trace systems has been in response to a perception that customers would want information on request concerning the progress of their consignments. In this way, the customers would be reassured that the transport service was working as expected. However, research by the authors has shown new possibilities which may have substantially greater appeal to transport customers. Track and trace systems, along with associated booking systems, are capable of generating databases with important potential applications. For example, by recording occurrences of transport system failure, management can be systematically alerted to the need to take action. Such databases can therefore make a key contribution to total quality management (TQM) programmes designed to improve services and, as a result, competitiveness. Similarly, databases information can be used to considerable effect in customer retention programmes. Information on the buying habits of customers can be the basis for differentiating service levels and pricing to match more closely the demands of customers. As competition in the European transport market intensifies it has never been more important for management to use data as creatively as possible to retain - or preferably expand - market shares.