Estimating the Maximum Production Rate Possible from Friable Sandstones Without Using Sand Control
Authors: Stein Nathan , Hilchie D.W. 
Published: December 2007

The technique described here makes it possible to avoid unnecessary sand-control measures. to indicate in economic terms when sand should be controlled, and to evaluate better whether existing sand-control measures are truly successful.

Introduction

Sand-production control in the oil industry has been a problem for more than 50 years. The incidence of sand-production problems in a well appears to be directly related to increased production rates. If the economics is such that high production rates must be maintained, sand may be produced continuously. Under such circumstances, control of sand is most readily achieved if measures are instituted early, before excessive sand is produced from the well. However, there are friable sand reservoirs in known sand-producing areas from which economically attractive production rates might be obtained without the use production rates might be obtained without the use of any form of sand control. This paper presents a method to estimate critical or maximum production rates possible without using sand-control measures. Such critical values represent limiting flow rates above which troublesome sand production is expected, not the maximum rate at which the well is capable of producing. producing. Approach to the Problem

To estimate the critical production rate it is necessary to (1) estimate formation strength from log data, (2) formulate the mechanism by which the formation face of a friable sand is rendered stable, and (3) apply the formation strength and stability mechanism considerations to well performance. A brief explanation of these three parts follows:

(1) formation strength may be estimated parts follows: (1) formation strength may be estimated from density and acoustic velocity log data, (2) the formation face is stabilized if sand arches form around each perforation and (3) critical production rates from sand intervals in an area can be estimated from one well production test in which reservoir pressure drawdown is production test in which reservoir pressure drawdown is increased in a sand of known strength until a sand problem occurs.

Formation Strength

Dynamically determined elastic modulus values of sands can be computed from the velocities of acoustic shear and compressional waves propagated through the sands. Data reported in the literature show that dynamic modulus values correlate with rock strength for a given class of material. Dynamic modulus values for sands adjacent to the wellbore may be computed from density and acoustic velocity log data, using the procedure given below. The acoustic velocity log procedure given below. The acoustic velocity log normally available gives only compressional wave data.

The calculations are based on the equation for the velocity of propagation of a compressional sound wave in porous medial in which a combination of bulk (E ) and shear (E ) modulus values are included.

(1)

Eq. 1 may be written in terms of density and acoustic velocity log values to provide the modulus combination in psi units:(2)

JPT

P. 1157