Bojan Moslavac

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.

Application of Artificial Clay Samples (Pellets) in Laboratory Testing of Shale/Drilling Fluid Interaction

Wellbore instability was and is one of the most frequent problems in petroleum industry, especially in the drilling operations. It is mainly caused by the shale formations which represent 75% of all drilled formations. The wellbore instability problems involve tight hole spots, wellbore diameter enlargement, the appearance of cavings, the inability of carrying out wireline operations, poor hole cleaning, unsuccessful wellbore cementing operations and other. The wellbore instability is the result of mechanical and physico-chemical causes mostly acting concurrently. The shale instability basically comes out of its mineralogical composition (especially clay minerals content) and physico-chemical properties. Shale-mud interaction includes water/ions movement in and out of the shales due to pressure differential, osmosis, diffusive flow and capillary pressure. Many research activities about shale instability causes and shale properties (affecting shale behavior) definition have been carried out by now. Different shale samples, laboratory equipment and inhibitive muds have been used. Laboratory tested shale samples are provided by the wellbore cores, surface sampling or, which is the simplest method, by collecting the samples at the shale shakers during drilling operation. The amount of these samples is not enough for laboratory testing. Another problem is closely connected to sample quality and preservation. There are also differences in drilling fluids used in these laboratory tests, especially in their composition (sometimes containing more than one shale inhibitor). It is difficult to compare test results and conclusions made by different authors. The laboratory study presented within this paper are done with artificial clay samples (pellets) made by compacting the powderish material containing exact quantity of quartz, montmorillonite and kaolinite. The laboratory testing is done by treating the powderish samples inside the desiccator (24 hours), compacting (30 minutes), swelling (24 hours) and drying samples (24-hour). Sample swelling is tested by using different mud types and the sample mass is measured in each above mentioned phase. Special attention is directed to preparation and pellets content definition as a good replacement for the original shale in laboratory testing of shale and drilling fluid interaction. The influence of used muds on the total pellet swelling and swelling intensity, especially at the early phase of testing was determined.Copyright

TESTING AND CHARACTERIZATION OF VULCANIZED NITRILE SWELLING ELASTOMERS

This paper describes preliminary methodology and characterization of the vulcanized nitrile butadiene rubber (NBR) samples submitted to swelling and mechanical testing. Nitrile rubber was used to study swelling processes of swelling packer sealing element. Five different compositions for a rubber vulcanization were used trying to build the best possible combination of components applying different concentrations of each component. Both swelling and mechanical testing were done at the room temperature. Rubber samples swelling was performed in oil acquired from one of Croatian oil fields. The other part of the testing sequence refers to tensile stress-strain tests to the point of break performed on dumbbell samples. Tensile testing was rendered on non-swollen rubber samples using a tensile testing apparatus. From the obtained results it can be seen that swelling process of the nitrile rubber strongly depends on cross-link density.© 2013 ASME

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.