A Method Of Monitoring Sand Production In A Flowing Well Stream
Authors: Foster Charles R. , Linville Thomas W. 
Published: December 2007

Control of sand production is a major concern in Sun Gas Company's offshore Gulf of Mexico operations. Sonic sand detection systems now in service on several Sun operated production platforms provide an effective, relatively low cost platforms provide an effective, relatively low cost method for maintaining optimum production rates while minimizing equipment erosion and well bore damage. A case history of field application on one Sun platform as well as the theoretical basis for the Sonic Sand Detector is presented.

Introduction

In June, 1978, Sun initiated operations on an offshore gas production platform in the East High Island Field. Initial rates ranged from 3 to 12 MMcf per day, with little or no liquids from each of twenty-six well streams. Initial pressures were 2,500 psi flowing and 3,000 psi pressures were 2,500 psi flowing and 3,000 psi static.

Due to economic and safety considerations, a sonic sand detection system was installed. The objective was to determine the maximum flow rate at which each well could produce free of sand.

The productive horizon in this field is Pleistocene at vertical depths of 7,000 - 8,000 Pleistocene at vertical depths of 7,000 - 8,000 feet. The directionally drilled wells have deviations up to 65 degrees and measured depths up to 12,000 feet. Dual completions with two strings of two-inch production tubing inside seven-inch casing perforated through tubing with four jet shots per foot predominate. Sand consolidation or gravel packing techniques were not applied to any of the wells.

THEORY

In the late 1960's, experiments were conducted at Mobil Field Research, Dallas, Texas by L.D. Mullins, W.F. Baldwin and P.M. Berrys in the detection and measurement of free-flowing sand in gas well applications. The Sonic Sand Detector is an outgrowth of the work of these men along with modifications by Dr. Paul Boatright of Oceanography International Corporation.

The Sonic Sand Detector (SSD) is designed to detect solids in flowing wells. Information obtained from the system is used to:Establish the maximum flow rate at which a well will produce free of sand.Provide an early warning when sand erosion conditions exist.Provide data on the effectiveness of various completion techniques.Calculate the rate of sand production.

The theory of operation of the SSD is relatively simple. When a moving particle strikes a stationary object, part of that particle's kinetic energy is converted to thermal energy and part to acoustic energy. The proportions of each type of energy are determined by the composition of the materials involved and the angle of incidence between the moving and stationary object.

The duration of the acoustic impulse generated is directly related to particle flexibility. The more flexible the particle, the longer the acoustic impulse. Similar frequency spectrums result, but the more flexible particle has more of its resulting energy concentrated at the lower end of the frequency spectrum. Particles of liquid, being more flexible, will predominate the lower end of the frequency spectrum up to about 300 kilohertz. Machinery and other man-made noise also contribute to the lower end of the spectrum. Solid particles predominate above 300 kilohertz. Figure 1 illustrates the approximate relationship of these factors.