Michael W. Sanders

Gravel Pack Designs of Highly-Deviated Wells with an Alternative Flow-Path Concept

Alpha-Beta gravel packing procedures have been used with a moderate degree of success in highly -deviated wells. Incorrect concentrations of gravel and/or pump rates can result in bridge formation in the open hole/screen annulus and Beta wave initiation prior to reaching the toe. If there is a high leakoff zone, gravel concentration will increase, and there may be insufficient velocity to trans port the solids farther down the well. Either factor or a combination of the two can lead to formation of a bridge in the openhole/screen annulus and an early initiation of the Beta wave. Other effects that could lead to bridge formation include: flow restriction and blockage from collapse of an unstable open hole section, and changes in annular velocity transition from one hole size to another. Incomplete gravel placement and the presence of voids around the screen can result from all of the complications described above. To overcome these, an alternative flow path system has been developed. If a bridge forms, the alternative path allows the slurry to bypass it. A number of physical models have been used to design and examine the effectiveness of the system, which has been validated in field applications. A numerical model has also been developed to assist with the gravel pack designs in highly-deviated wells. The model simulates the alternative flow -path concept as well as conventional gravel packing in open hole or cased -hole completions of arbitrary deviation. Details of the alt ernative flow -path scheme as well as the formulation of the numerical model are presented in this paper. Simulation results were compared to observations in the physical models.

Remediation of Proppant Flowback-Laboratory and Field Studies

This paper presents the results of laboratory studies and field case histories of a remedial treatment technique using a lowviscosity consolidation fluid system that is placed into the propped fractures by coiled tubing (CT) or jointed pipe coupled with a pressure pulsing tool. The treatment fluids are designed to provide consolidation (for previously placed proppant) near the wellbore to glue the proppant grains in place without damaging the permeability of the proppant pack. Laboratory flow testing indicates that the proppant pack in a fracture model under closure stress only requires lowstrength bonds between proppant grains to withstand high production flow rates. The consolidation treatment transforms the loosely packed proppant in the fractures and the formation sand close to the wellbore into a cohesive, consolidated, yet highly permeable pack. Field case histories are presented and the treatment procedures, precautions, and recommendations for implementing the treatment process are discussed. One major advantage of this remedial treatment method is the ability to place the treatment fluid into the propped fractures, regardless of the number of perforation intervals and the length of the perforated intervals without mechanical isolation between the intervals. The fluid placement efficiency of this process makes remediation economically feasible, especially in wells with marginal reserves.

Planning, execution and verification of a coiled tubing gravel pack job in the Statfjord field

This paper describes the initial planning and pre-job laboratory testing for a gravel pack operation using coiled tubing in the Statfjord Field. The paper also describes the execution of the operations and methods involved. Potential problems related to the placement of the gravel were identified in pre-job meetings and were verified through a comprehensive test programme. A well specific cased hole completion was modelled using an acrylic gravel pack simulator, and a number of tests were performed to determine the optimum solution for gravel concentration, brine viscosity, viscosifier and slurry placement rate. The tests were utilised as an aid in designing the actual gravel placement operation. The gravel packing operation was conducted using small batches of slurry consisting of a non-viscosified brine carrier fluid along with a low gravel concentration. Two separate radioactive tracers were injected into the slurry to give better resolution of the gravel pack logs. The operation and completion technique is reviewed and verified by extensive post completion analysis. This includes calculated sand height verified by gravel pack placement logs. Initial gravel pack productivity is comparable to conventionally gravel packed wells.