Openhole gravel packing is one of the popular completion techniques in challenging, high-transmissibility reservoirs. Many of such wells are drilled with synthetic fluids and completed with either a single-or a two-trip technique.In single-trip approaches, the entire wellbore is displaced to water-based fluids before running screens and subsequent gravel packing. Although successful in some cases, this technique has been problematic in reactive-shale environments because of problems in screen installation to target depth, resulting from shale swelling and/or collapse. Such problems led operators to a twotrip approach in which a predrilled liner is installed in syntheticbased mud (SBM), displacements are performed to water-based fluids, and the screens are run in a solids-free (SF) water-basedfluids environment, followed by gravel packing. In recent years, another approach was introduced, in which the displacements to water-based fluids are performed after the screens are installed in conditioned mud and the packer is set, followed by gravel packing with a water-based fluid. Although this approach eliminates the difficulties associated with screen installation as well as allowing a single-trip completion (no predrilled liner), it cannot be used in cases where conditioning is impractical.In this paper, we present case histories where screens were installed after the open hole was displaced to a solids-free SBM and the cased hole was displaced to completion brine, and gravel packing was performed using a water-based carrier fluid. This approach provides a cost-effective alternative to displacement of the entire wellbore to SF-SBM as well as eliminating the risk of screen plugging, and it was implemented successfully on two oil producers in Oyo field. Details of design, execution, and evaluation for drilling and completion stages, as well as well productivity measures, are provided. Review of the Practices to DateMany of the deepwater developments in West Africa use SBMs for both upper hole and reservoir drilling, and almost all of them require some form of sand control, openhole gravel packing being one of the widely used techniques. Gravel packing in SBM environments evolved substantially over the years, with a variety of options that can be categorized on the basis of the type of carrier fluid used for gravel packing [note that the terms SBM and oil-based mud (OBM) are used interchangeably in the context of this paper].Oil-Based Carrier Fluid. In this approach, the screens are necessarily installed with oil-based fl uids in the entire wellbore, where the wellbore fl uids can be any combination of (a) conditioned SBM, (b) fresh SBM (no cuttings), and (c) SF-SBM or oil-based carrier fl uid. The conditioned-SBM approach requires that the mud be passed through shaker-screens of suffi ciently small openings to prevent plugging of sand-control screens during installation and subsequent operations. As such, the type of screens used in the completion (wire-wrap or premium/metal-mesh) and the size of screen openings, and t...

The sand control completion is the last step in the well construction. It is the step that turns the well from an expense to a revenue generating asset. While every sand control completion is designed for success, things don't always go to plan during the installation, and the technical and commercial results are sometimes less than perfect. Failures can range from minor issues that can be easily remedied to catastrophic events that put the entire well, and investment, at risk. Regardless of severity, it is critical that all failures are analyzed to determine the root cause, prevent them from being repeated and protect asset value. The success of a sand control installation should not be assumed and can only be confirmed with a thorough review of all available job data. This paper introduces several case studies of failures that occurred during sand control installations and details the investigative process and techniques used to identify the root causes. Examples include events such as screen/wash-pipe damage, bridging, hole collapse, and packer seal failure. This analysis provides key insights into downhole events and mechanisms that can be used to minimize risk and improve future completions.

Openhole gravel packing is one of the most popular completion techniques, due to its high reliability along with the ability to deliver high-productivity wells. Currently, there are two techniques used for gravel placement, one utilizing low-viscosity carrier fluids and low gravel concentration. In this technique the gravel is placed in two waves commonly called Alpha/Beta packing. The second method utilizes a viscous carrier fluid and high concentrations of gravel in conjunction with alternative path screens which mitigate problems caused by unpredicted downhole events. In this paper we present a new approach for gravel packing long high angle openhole intervals without the need for alternative flow path screens but retaining the advantages of high gravel concentration slurries. This is supported by 2 field case histories from a field in India, where two gas wells were drilled with an oil-based drill-in fluid and gravel packed with a viscous water-based fluid. The packing mechanisms and efficiencies in these applications have been verified with downhole gauge analysis as well as mass balance calculations. Both wells are producing sand free with hydrocarbon production that met or exceeded operator expectations, with zero mechanical and extremely low rate dependent skins. Introduction Openhole gravel packing is one of the most popular completion techniques, particularly in deepwater developments with high transmissibility, due to its ability to deliver reliable, high productivity wells.1,2 Current techniques used for gravel packing horizontal wells include Alpha/Beta,3 Alpha/Alpha4 and Alternate Path packing.5 The first two techniques use a low viscosity carrier fluid (typically brine) with a low gravel concentration (typically 1.0 ppa). In both techniques, initial packing takes place in the lower part of the horizontal well until the bottom is packed all the way to the toe (called the Alpha Wave), if circulation can be maintained. This part is dominated by settling of the gravel up to an equilibrium height which is controlled by the circulation rate, with higher rates leading to lower bed heights. In the Alpha/Beta technique, the circulation rate is kept constant, and the packing proceeds from toe-to-heel, covering the upper part of the horizontal well (called the Beta Wave), once the Alpha Wave reaches the toe. For typical Alpha Wave height designs used in these treatments (barely covering the screens), pressure increase during the Alpha Wave is negligible, although the pressure rise during Beta Wave can be substantial. This is because of the narrow annulus between the screen base pipe and the wash pipe, through which the carrier fluid must travel and reach to the entry point into the wash pipe for returns to surface. Such pressure rise can be problematic in cases where the operating window between downhole circulation pressure and the fracturing pressure is narrow. Various hardware and chemistry solutions exist to overcome this problem, including diverter valves that are activated sequentially creating a new entry point upstream into the wash pipe,6 light weight gravel which allows lower pump rates for the same alpha-wave dune height as in conventional gravel7 and drag reducing additives that can be used in the carrier fluid either throughout the treatment or during the Beta Wave.8

While the importance of pre-job design has always been appreciated, detailed post-job evaluation of gravel pack execution data (both surface and downhole) is equally valuable as it provides a means to learn from past treatments, calibrate models, and improve future designs. Traditionally, post-job analysis has been limited to high-level pack evaluation and failure investigation but has a much wider range of applications in the confirmation of success, better understanding of downhole mechanisms and validation of simulation models. Downhole data analysis techniques can be used to isolate sections of the flow path and develop a more detailed understanding of each stage of the treatment from running in the hole (RIH) to pulling out of the hole (POOH). Detailed post-job evaluation is often skipped due to the significant effort involved in data handling as well as the lack of a defined workflow and an integrated software tool. This paper provides an overview of the evaluation and calibration of surface and downhole data along with the steps, workflow and tools required to process the data in the easiest and most efficient manner, enabling faster, more detailed and more accurate analysis of operations. Various case studies are used to demonstrate how post-job evaluation using downhole gauges can be used to efficiently analyse the various stages of the operation including wellbore displacements, reverse and circulating step rate tests and gravel packing operations. A variety of important phenomena are identified and quantified, such as friction pressures, packing mechanisms, fluid displacements, screen plugging and roping, which may otherwise be missed. The paper further illustrates how the defined workflow can maximize the likelihood of success by using post-job evaluation results to better identify and minimize risks during pre-job design stages while reducing the need for excessive safety factors within the operational window. The analysis workflows introduced here will maximize the value of downhole gauge data and serve as a reference to practicing completion engineers in the efficient processing, analysis and interpretation of post-job data. It can be used to revisit and better understand historical sand control treatments, and continuously improve future treatments.

Proper design, installation and evaluation of sand control completions is vital for ensuring sand control integrity and mitigating against production deferrals due to sanding events. This is becoming increasingly important in the ACG Field, located offshore Azerbaijan, where wells require gravel pack completions with shunt tube technology and narrow operating windows between reservoir and fracture pressures. However, due to the lack of suitable commercially available software and a standardized workflow, gravel pack operations have been designed and evaluated using a combination of customized spreadsheets, historical data and software ported from other industry segments, none of which support the complex flow paths, conditions and range of technology utilized. While this did work, it was a time-consuming and inefficient process that required a number of assumptions and continuous data transfer which could allow for inconsistencies when applied at scale with an increasing number of users. To improve and standardize the design and evaluation of wells in the ACG field, a novel, commercially available sand control software was introduced for performing pre-job modelling, on-the-job calibration and post-job analysis in an integrated workflow for all stages of the sand control operation including wellbore displacements, step rate tests, gravel pack and reverse out. The software supports all common sand control technologies and flow paths, enabling the determination of optimal completion and hydraulic configurations during planning, identification of potential issues and redesign of the treatment during installation, as well as automatic analysis of surface and downhole data for a more detailed understanding of downhole events and mechanisms during post-job evaluation. This integrated workflow is presented using case studies from the ACG field to illustrate its application and benefits. The workflow is found to be simpler, more effective and more accurate than the techniques used in the past, enabling all necessary modeling to be quickly and easily performed in-house for improved planning and optimization of upcoming operations. Further, the automated analysis of surface and downhole gauge data enabled detailed evaluation to be completed in a timely manner which maximized the value of the acquired data and ensured lessons learned could be effectively implemented. Finally, the ability to directly compare simulated and actual treatment data allowed the engineers to calibrate and validate the model for more accurate modelling of future treatments.