Summary Openhole sand-control technique selection has been a topic of interest since the late 1990s and was discussed most comprehensively in SPE 85504 (Price-Smith et al. 2003), which proposed guidelines for selection between standalone screens (SASs), α/β packing, and shunt-tube packing. Proposed guidelines were based on formation characteristics such as formation strength, particle-size distribution (PSD), mineralogy across the well path; risk factors involved in execution as well as reliability/longevity; and cost considerations. From a PSD standpoint, their guidelines were based on the criteria proposed earlier in SPE 39437 (Tiffin et al. 1998), whereas risk evaluation was based on the technologies available at that time. Since then, significant advancements were made in understanding sand-retention mechanisms and failure modes of SASs, and in technology development to extend the limits of openhole gravel packing. These combined with the field experience in the last decade certainly warrant re-examination of their guidelines, which is the objective of this paper. In this paper, we begin with a critical review of the current sand-control technique-selection methodologies for openhole completions, including the way some of the risk factors are being evaluated to eliminate a given completion technique. On the basis of the technologies developed in the last decade, we propose a new approach for selecting sand-control technique, along with techniques/tools for proper evaluation of the risk factors. The proposed approach significantly extends the application limits of SASs and α/β packing compared with what was proposed in SPE 85504 (Price-Smith et al. 2003).
Gravel packing is increasingly used in long horizontal wells and challenging environments. Key to executing the gravel-pack job successfully is selecting an appropriate gravel-carrier fluid. Frictional pressure loss exhibited by gravel-packing fluids is an important consideration in their selection. This paper discusses the friction pressure performance of commonly used gravel-packing fluids in the industry today, which include the viscoelastic surfactant (VES) types of fluids, xanthan, and hydroxyethyl cellulose (HEC).In wells with a long horizontal section or narrow margin between pore pressure and fracture gradients, the frictional pressure loss exhibited by these fluids in the wash pipe and washpipe/base-pipe annulus governs whether these wells can be gravel packed without fracturing the formation. In gravel packs with alternative-path configuration (shunts), the frictional pressure loss through the shunts controls the maximum length that can be gravel packed.This paper discusses in detail the fluid friction pressure performance while pumping these fluids through various conduits including circular pipe, eccentric annuli, and rectangular tubes (shunts). These data were generated in field-scale yard tests under controlled conditions, for both ambient and elevated temperatures. The paper also discusses the rheological properties of these fluids at ambient and elevated temperatures. The effect of factors such as surfactant/ polymer concentration, addition of gravel, and temperature on the frictional pressure loss of these fluids is presented, which will help in fluid selection/optimization under different scenarios.
Gravel packing is one of the commonly used sand control techniques in long openhole horizontal completions. Although numerous wells have been gravel packed with either one of the two placement techniques (α/β or shunt tubes), achieving a complete pack with sand control screens that have inflow control devices (ICD) can be challenging to say the least. This is because of the high pressure drops needed for the fluid to flow through the ICD into the base-pipe/wash-pipe annulus at the typical rates used for gravel packing, resulting in significant pressure rise and exceeding the fracturing pressure of the formation. Although using a screen without an ICD at the bottommost joint would certainly allow the α-wave to reach the toe, the pressure buildup will occur as soon as the β-wave proceeds upstream of that joint, which will either result in formation fracturing and bridging or significant rate reduction and α-wave height increase (near the heel first), both events resulting in a premature screenout. Ocelote field in Colombia requires sand control, and gravel packing and standalone screens (SAS) have both been used in openhole horizontal completions in various parts of the field. An additional challenge in this field has been the premature water breakthrough from the aquifer leading to very high water cuts after only a few months of production. ICDs have successfully been implemented in SAS completions to address this challenge in other parts of the world. Similarly, gravel packing has been successful in controlling sand in parts of the field where SAS was considered unsatisfactory, although water cut in most of these wells increased to 70 to 90% after only 3 months of production. In this paper, we present a novel technique for wells that require gravel packing for sand control and ICD functionality for managing water encroachment. Detailed in the paper is the first application of the proposed technique in Ocelote field, which resulted in 100% pack efficiencies using the water packing technique as well as significant reduction in water cuts, with substantial improvement in the project economics.
The term DLC (diamond-like carbon) describes a whole class of different biocompatible materials based on amorphous carbon. One possible application for DLC is the coating of artificial hip joints to increase their life expectancy. The life expectancy of artificial hip joints is limited by osteolysis caused by wear particles, especially by wear particles in a range from 0.3 lm to 10 lm. In this study, biocompatible steel substrates are coated with DLC. Coatings with different structure are produced and investigated regarding their wear behavior. The aim is to influence the wear particle size distribution. To improve the adhesion of the coatings on the substrate, metallic interface layers are deposited by cathodic vacuum arc deposition, comparing chromium and titanium as interface layer material. The DLC-coatings are deposited by a vacuum arc that allows a transition from cathodic to anodic operation mode.It is shown, that by varying the deposition process parameters and thus by variation of the film properties, the wear particle size distribution can be adjusted significantly. Es konnte gezeigt werden, dass durch Variation der Parameter beim Abscheiden die Größe der Abriebpartikel gezielt beeinflusst werden kann. Dem Ziel, Abriebpartikel kleiner als 0.3 lm zu erhalten, wurde bedeutend näher gekommen.
Sand control technique selection in open holes has been a topic of interest since the late 90s and discussed in many papers, most comprehensively by Price-Smith et al. (SPE 85504) who proposed guidelines for selection between standalone screens, α/β packing and shunt tube packing. Proposed guidelines were based on formation characteristics (formation strength, particle size distribution, mineralogy across the well path, etc.) as well as risk (execution, reliability/longevity, etc.) and cost considerations. From a particle size distribution standpoint, their guidelines were based on the criteria proposed earlier in SPE 39437 (Tiffin et al. 1998), while risk evaluation was based on the technologies available at that time. In this paper, we begin with a critical review of the current sand control technique selection methodologies for open-hole completions, including the way some of the risk factors are being evaluated to eliminate a given completion technique. Based on the technologies developed in the last decade, we propose a new selection methodology along with techniques/tools for proper evaluation of the risk factors. The proposed methodology significantly extends the application limits of standalone screens and α/β packing compared to what was proposed in SPE 85504 (Price-Smith et al. 2003).
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