Perforation Collapse Research Articles

Design for Reliability: Experimental and Numerical Simulation of Cased and Perforated Completions with Standalone Screen

Summary The historical challenges and high failure rate of using standalone screen in cased and perforated wellbores pushed several operators to consider cased-hole gravel packing or frac packing as the preferred completion. Despite the reliability of these options, they are more expensive than a standalone screen completion. In this paper, we employ a combined physical laboratory testing and computational fluid dynamics (CFD) for laboratory scale and field scale to assess the potential use of the standalone screen in completing the cased and perforated wells. The aim is to design a fit-to-purpose sand control method in cased and perforated wells and provide guidelines in perforation strategy and investigate screen and perforation characteristics. More specifically, the simultaneous effect of screen and perforation parameters, near wellbore conditions on pressure distribution and pressure drop are investigated in detail. A common mistake in completion operation is to separately focus on the design of the screen based on the reservoir sand print and design of the perforation. If sand control is deemed to be required, the perforation strategy and design must go hand in hand with sand control design. Several experiments and simulation models were designed to better understand the effect of perforation density, the fill-up of the annular gap between the casing and screen, perforation collapse, and formation and perforation damage on pressure drop. The experiments consisted of a series of step-rate tests to investigate the role of fluid rate on pressure drop and sand production. There is a critical rate at which the sand filling up the annular gap will fluidize. Both test results and CFD simulation scenarios are comparatively capable to establish the relation between wellbore pressure drop and perforation parameters and determine the optimized design. The results of this study highlight the workflow to optimize the standalone screen design for the application in cased and perforated completions. The proper design of standalone screen and perforation parameters allows maintaining cost-effective well productivity. Results of this work could be used for choosing the proper sand control and perforation strategy.

Modeling Borehole and Perforation Collapse with the Capability of Predicting the Scale Effect

In this paper the writers examine a borehole failure model that is based on fracture mechanics and layer buckling theories and compare its predictions with experimental data. The model assumes that the main failure mechanism of borehole collapse takes place in the form of (preexisting or formed) layers buckling. The model introduces a combination of fracture mechanics parameters with length dimension that scales the size of the holes, thus allowing for size effect predictions. The writers review the model and compare its predictions with available experimental data of hollow cylinder tests on weak rocks. The writers found for the model predictions and for the experimental data a strong correlation between hollow cylinder strength normalized by the rock strength and hole size normalized by the square of the ratio of fracture toughness over tensile strength. These findings can be used for constructing efficient mechanical models for predicting or interpreting failure of boreholes and perforations in mining and petroleum engineering.

Challenges, Accomplishments, and Recent Developments in Gravel Packing

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized to be experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Introduction Techniques used for sand control include restricted hydrocarbon production, in-situ consolidation, gravel packing, high-rate water packing, frac packing, fracturing without screens, and drilling horizontal wells completed with screens. Frac packing, high-rate water packing, and horizontal completions have been the most widely used of these techniques in recent years. Fracturing without screens, frac packing, and horizontal drilling all aim at reducing drawdown and/or increasing production rates by decreasing velocities in the formation with a larger flow area. The increased flow area also makes these methods more tolerant to formation and completion damage. Achieving long-term sand control without impairing well productivity has been a challenging task from both a technical and an economic perspective for many years in almost all major oil- and gas-producing regions of the world. Because this article is a review of the challenges, accomplishments, and recent developments in gravel packing, we limit our discussion to treatments below fracturing pressure by assuming that exceeding the fracturing pressure is undesirable for technical reasons. It is not our intent to suggest that gravel packing is the preferred sand-control method. All methods for sand control have their own applications and value in the industry. We first discuss recent developments and challenges in gravel, screen, and carrier-fluid areas and follow this by a discussion of gravel packing in cased holes, where major accomplishments have been introduction of combined processes that not only reduce completion costs but also improve productivity. Next, were view openhole gravel packing, primarily for highly deviated or horizontal wells because this is where most openhole gravel-packing applications have been. Finally, we draw conclusions and highlight the accomplishments and remaining challenges. Ideal Gravel-Pack Completion From a technical standpoint, an ideal gravel-pack completion accomplishes the following objectives.Complete packing, with a properly sized high-permeability gravel, of allvoid spaces between the screen and casing and perforations or between the screen and the open hole.Clear interface between the formation sand and gravel, with nomixing/invasion of formation material with/into the gravel pack during placement and during production throughout the life of the well.No invasion of the matrix with damaging material (e.g., unfiltered or incompatible brines, polymers, crushed gravel).No reduced-permeability section between the formation sand and the gravelpack (e.g., drilling-fluid filter cake in open holes or crushed zone in cased and perforated holes).No residuals from the carrier fluid and/or fluid-loss pills (e.g., polymers and bridging agents in gravel pack). Particular attention also must be given to prevention of screen plugging while running the screens in hole (discussed later). Obtaining a technically ideal gravel pack as described has been a major challenge, and all objectives have not been achieved under all circumstances. Furthermore, achieving this type of completion may not always be necessary, depending on cost/benefit analysis. For example, openhole horizontal completions sometimes can tolerate high levels of damage with little impact on productivity. In such cases, incremental production resulting from a cleanup treatment needs to be weighed vs. cost. Regardless of the type of completion (open or cased), the first potential source of formation damage is the drilling fluid. In recent years, with the increased applications of horizontal wells, substantial effort has been devoted to formulating reservoir drilling fluids (RDF's) that form a tight filter cake with minimal particle and polymer invasion into the matrix and that contain soluble (in acid, water, or oil) bridging agents. Proper RDF selection typically is considered to be less of an issue in cased holes because the damaged region is believed to be bypassed by the perforations; however, this may not be true in unconsolidated sand formations because perforation collapse is highly likely.