Formation damage caused by drilling-fluid invasion, production, or injection can lead to positive skin factors and affect fluid flow by reducing permeability. When mud filtrate invades the formation surrounding a borehole, it will generally remain in the formation even after the well is cased and perforated. This mud filtrate in the formation reduces the effective permeability to hydrocarbons near the wellbore. It may also cause clays in the formation to swell, reducing the absolute permeability of the formation. In addition, solid particles from the mud may enter the formation and reduce permeability at the formation face.

A sand control completion that uses a screen and a gravel pack to stop formation sand production.

The earliest gravel packs were performed in shallow, vertical wells, typically by simply pouring gravel into the tubing/casing annulus and allowing the gravel to settle around a screen. Some screens were even washed into place after the gravel was placed. The technique is still employed in water wells but now is seldom used in oil/gas wells. As equipment and technology improved, gravel packing of oil/gas wells was accomplished by mixing sand in brine and pumping the mixture into the hole. Brine represents the simplest of the transport fluids.

A gravel pack is simply a downhole filter designed to prevent the production of unwanted formation sand. The formation sand is held in place by properly sized gravel pack sand that, in turn, is held in place with a properly-sized screen. To determine what size gravel-pack sand is required, samples of the formation sand must be evaluated to determine the median grain size diameter and grain size distribution.[1] The quality of the sand used is as important as the proper sizing. The American Petroleum Institute (API) has set forth the minimum specifications desirable for gravel-pack sand in API RP 58, Testing Sand Used in Gravel-Packing Operations.[2] The first step in gravel-pack design is to obtain a representative sample of the formation.

An operator successfully executed two wireline through-tubing gas-shutoff (GSO) workovers in high-angle openhole-gravel-pack (OHGP) completions to isolate high-gas/oil-ratio (HGOR) zones, resulting in significantly increased oil production.

You must log in to edit PetroWiki. Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. A sand control completion for high permeability soft sand formations where the small amount of area offered by the perforations is a restriction on what the formation can deliver to the wellbore.

Abstract Open hole gravel packing (OHGP) is one of the primary completion techniques in sandstone reservoirs with sanding tendencies. As companies are becoming more experienced with these operations they are starting to explore the options for completing more challenging wells; including longer open holes and more tortuous trajectories. Conventional techniques have limits when it comes to the maximum length and angles that can be gravel packed based on a defined set of parameters. In order to ensure the success of the gravel packing operations in these challenging wells new techniques need to be adopted. This paper includes a review of the methods that can be utilised to extend the operating limits of open hole gravel packs, so that they can be used in the long geosteered wells that are becoming more common in the North Sea. It includes a case review of the first well gravel packed in the North Sea using Ultra-Lightweight (ULW) proppant, which was also the first ever combined use of ULW proppant and diverter valves. These technologies were required due to the long interval length, 4,880ft, and high angle, maximum 103°. A history match of the gravel pack model was also performed to evaluate the performance of the ULW proppant during a long horizontal gravel pack.

Abstract A 7-in. single-trip multizone (STMZ) gravel pack system was installed successfully in two wells in the T field, Sarawak offshore. This paper highlights the system performance and knowledge obtained during this first-time installation performed in Malaysia. The most common sand control techniques established in the H, I, and J sands of this mature field include stacked gravel pack, 9 5/8-in. single-trip multizone gravel pack, and openhole standalone sand screen (OHSAS) systems. Internal gravel pack completions have provided proven, robust sand control for the sand-prone reservoirs in the T field and can save four to five days of rig time depending on the well configuration, compared with the standard stacked gravel pack completion, which was initially planned during the field development plan (FDP) stage. This paper presents the extensive technical works performed post-FDP approval to ensure the change from the 7-in. stacked gravel pack to the 7-in. single-trip multizone gravel pack completion was executed safely and efficiently and most importantly able to maximize the recoverable reserves from the multiple unconsolidated reservoirs. The technical challenges, such as unexpected drilling of additional zones, limited annulus clearance between the 7-in. liner and gravel pack tool string to reverse out proppant efficiently, intersands spacing, and gross sand interval constraints within certain tolerance because of bottomhole assembly (BHA) limitations, are also discussed. The 7-in. single-trip multizone gravel pack installation helped reduce rig time and provided a cost savings of nearly USD 1.1 million. Subsequently, the two oil-producing (OP) wells (two OP wells and four OP strings) are producing sand-free at higher than expected reserve and flow rates.

Openhole gravel pack is the preferred completion method of sand control in unconsolidated deepwater formations with sanding tendencies. The design phase of an openhole gravel pack treatment spans drilling of the reservoir section, wellbore preparation, sand screen installation, gravel placement, and well flowback. This paper discusses several ultra-deepwater wells of India, where openhole gravel packs were performed by integrating drilling, wellbore cleanout, wellbore displacement and gravel pack methodologies to achieve a holistic approach towards openhole gravel pack completions.

The reservoir sections were drilled with streaks of shale and dolomite sections, the liner shoe often landing in shale, exposing a shaly rat hole. Next, the wells were displaced to dedicated production screen testing (PST) mud prior to running in screens. Screens were then placed across the openhole with memory gauges to capture downhole events during the gravel pack. The displacement pills train was engineered to displace the open hole with water-based fluid prior to starting the gravel-pack treatment. Extensive lab testing and displacement simulations for efficient spotting of pills and optimal sweeping effect were performed. The gravel-pack treatment was executed using Alternate Path technology and a high-temperature viscoelastic surfactant (VES) carrier fluid system.

11 ultra-deepwater wells off the east coast of India were completed. Displacement of open hole from drilling fluid to water-based system was done with direct displacement and reverse displacement methods. Due to the narrow fracturing window of 200-300 psi in all the wells, bottomhole pressures were managed by deploying multiple techniques such as using a lighter VES-based brine, optimizing the rheology of the fluid and taking returns through the riser. Roping behavior of the pre-pad and slurry have also been studied, and results presented to correlate with design. All open-hole gravel packs were executed without losses and achieved complete packs. Finally, flowback and well test data were analyzed by the operator and found to be as expected with no sand ingression. A holistic approach toward open-hole gravel-pack treatments has been developed, analyzing all the interlinked elements and the efficacy of the design process verified against surface and downhole data gathered for each well.

This paper discusses the approach, simulations, lab testing, and evaluation, analyzing captured data from drilling phase of the open hole to completing the well by placing gravel across the screens and flowing back. The design approach, integration strategies, and lessons learned in these wells offshore India can be applied to improve success rates of sand control completion wells around the world.

Achieving complete and efficient gravel packing is the primary objective when tasked to install an effective sand control completion. This paper describes the challenges faced during the selection, design, planning and execution phases of the open-hole horizontal gravel pack completions in the "L" field, offshore Republic of Congo. The open hole gravel packs (OHGPs) targeted the most prolific sand to ensure production objectives were achieved with the benefit of a gravel-pack completion.

The operator completed two OHGPs with alpha/beta technique for the sand face completion utilizing concentric annular pack screen (CAPS), wire-wrap screens, and a service tool permitting post-gravel pack filter cake clean-up treatments. The accurate selection, modeling, and evaluation of sand control techniques were crucial for completion and production optimization, as well as risk minimization. The service approach had traditionally leveraged upon industry rules of thumb and previous experience, but as the reservoir section length increased and completion configuration became more complex, the error margins tightened and the cost of failure increased such that a more robust design approach was needed.

This paper addresses several key factors that must be considered carefully when installing a successful gravel pack completion. The dynamic pressure management becomes critical to maintain the bottom hole pressures within a required range for the successful implementation of the gravel pack. Other factors include designing an optimal screen-wash pipe annulus ratio during alpha-beta wave packing, an optimal alpha wave height, and the use of multiple beta wave packing rates.

Results from the preliminary modelling of the gravel pack pumping provided an accurate estimation of the maximum and minimum anticipated pumping rates and pressures. These parameter estimates were generated for the workstring design scenarios and provided guidance for the planned pumping rate adjustment during the gravel packing execution phases. The gravel packed wells achieved pack efficiency greater than 100% based on an estimated 8.5-in. diameter OH. Post completion multi-rate tests concluded potential productivity exceeding the operator's expectations.

This paper describes the lessons learned and best practices developed for offshore Congo open-hole gravels packs, which have a very challenging well completion and reservoir scenario. Several proven completion practices are reviewed, with a critical examination of the application of these scenarios for future completion operations in this difficult operating environment. This applied methodology has made significant impact on future field development and increased the production expectations for the asset.