Controlled Injection of Sand Consolidation Plastic
Authors: Strohm Paul J. , Mantooth M.A. , Depriester C.L. 
Published: December 2007

A new placement system for sand consolidation plastic has been developed to increase success ratios and to extend use of plastic to sands with variable permeability, dirty sands and long or discontinuous completion intervals. Plastic sand consolidation fluids are distributed uniformly through a series of fluid flow control modules with each module covering 2 ft of completed interval. Active modules can be separated by blank spacers to cover a number of individual completed sections in a total interval of 50 ft. Further development is in progress to cover longer intervals. Equipment operation, perforation control and completion program recommendations are discussed. The system has been used in about 75 completions covering up to five individual sand members in total intervals up to 41 ft. Successful plastic sand consolidation has been obtained in many sands where other sand control methods were unsuccessful. Use of the new plastic injection system improves development economics in sand problem areas in three important ways:better fluid injection control increases completion success ratio,greater placement reliability permits reduction in chemical cost and pumping time andone-trip coverage of discontinuous zones significantly reduces completion cost compared to a series of individual packer settings.

Introduction

Achieving uniform placement of injected fluids into the formation around the wellbore has long been a problem. Success of nearly every injection process is directly dependent upon the degree to which uniform placement is achieved and plastic sand consolidation processes are no exception regardless of chemical and procedural differences. All such processes should provide adequate distribution of consolidating materials around the wellbore to achieve success. Assuming a good cement bond and clean perforations, poor distribution of injected fluids is due principally to permeability differences that occur throughout a formation interval. The composite log with core analysis data (rubber sleeve core) in Fig. 1 shows permeability variations that occur in a typical offshore Louisiana well in Miocene sediments. Note that variations of several hundred millidarcies occur within relatively short increments of the total interval. The lithology column in Fig. 1 is of particular interest because it shows how the grading from claystone to silt to sand takes place over short distances in the geologic column. These thin siltstone and claystone sections may not be seen on conventional logs, but they affect fluid injection patterns and point up the need for plastic sand consolidating processes that are not adversely affected by clays. To reduce the effects of permeability variation, most successful plastic sand consolidation efforts to date have been limited to comparatively short intervals. Review of an article on plastic sand consolidation results in 1959 and an article on the subject as recently as Feb., 1966, discloses that the greater number of successful plastic sand consolidation jobs have been accomplished within intervals of 10 ft or less. Longer intervals were consolidated with separate straddle operations or with a staging procedure. For example, the well shown in Fig. 1 could be consolidated with three separate treatments using retrievable squeeze tools and bridge plugs. Results of attempting to straddle too long an interval are shown in Fig. 2. Consolidation of discontinuous intervals presents a problem. This condition is indicated in the well log shown in Fig. 3. This log shows an interval some 40 ft long containing five productive sand stringers ranging from 1 to 4 ft in thickness. The successful consolidation of these sands might require five separate straddle operations with previously available methods. In summation, a need existed for better control of sand consolidation fluid injection throughout long producing intervals, including discontinuous sands, and preferably in a one-round-trip operation. Solutions to these problems wouldpermit a reduction in the amount of plastic required,permit the consolidation of long intervals,permit economic consolidation of discontinuous intervals.lower costs andincrease success ratios.

Development of improved injection control equipment was a necessary part of research to provide an improved plastic sand consolidation system. Closely related work to develop an improved sand consolidation process has been presented.

JPT

P. 487ˆ