Unconsolidated Sand Stabilization Through Wellbore Stress State Control
Authors: Suman George O. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

This paper was prepared for the 50th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Dallas, Texas, Sept. 28-Oct. 1, 1975. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting end, with the paper, may be considered for publication in one of the two SPE magazines.

Two methods are presented for controlling wellbore stress state in order to stabilize unconsolidated sands. One method is the application of elevated drilling fluid weight to prevent dilation and/or shear/crushing of sand grains surrounding the wellbore. Instabilities resulting from such formation failure would be expected to increase the likelihood for sand production. Means are provided for determining mud weight required to avoid such failure. provided for determining mud weight required to avoid such failure. The second method suggests that there is an elevated range in stress state in which stable sand arches will form over perforations and permit unrestricted production flow rates from perforations and permit unrestricted production flow rates from many wells without sand production. The method utilizes one or more inflatable external casing packer(s), opposite the intervals to be perforated, for establishing and maintaining the proper stress state for stable sand arches.

Introduction

This paper suggests that unconsolidated sands may be stabilized, and sand production avoided, through (1) use of elevated drilling fluid weight to prevent dilation and/or shear/crushing failure of formations during drilling and (2) application of inflatable external casing packers within the interval to be perforated to establish and maintain stable sand arch loads. Support for these concepts is provided through interpretation of sand arch experimentation, considerations of the state of stress at the wellbore face and general field observations. Field testing has not yet been undertaken and cannot, therefore, be reported upon at this time.

The concepts discussed in this paper suggest that certain procedures commonly followed during drilling operations may harm procedures commonly followed during drilling operations may harm well performance during production operations. The suggested revised procedures to some degree run counter to the primary objective of most drilling groups which is to deliver a cased hole in the ground at least cost. Field application of these techniques will therefore require close cooperation between drilling, completion, and production personnel and the support of management.

INTERPRETATION OF SAND ARCH EXPERIMENTATION

Experiments on the arching behavior of sands under conditions encountered in producing wells have been extremely limited.