Effect of Water Cut on Sand Production—An Experimental Study

Abstract

Summary It is commonly acknowledged in the petroleum industry that water cut increases sand-production risk, and a number of possible mechanisms have been proposed. This paper presents the results of a series of laboratory perforation-collapse tests aimed at demonstrating and quantifying the water-cut effect on perforation failure and sand production. The laboratory perforation-collapse tests were conducted on weak sandstones obtained from downhole and outcrop. The tests were performed under simulated in-situ effective stresses and drawdown conditions. Water was introduced into the flowing stream of either oil or gas at various stages of the tests to simulate water cut. The failure and sand-production processes were observed and recorded using a borescope in real time. The results showed that the effect of water cut on perforation strength and sand production depends on the mineralogical composition of the sandstone and the degree of residual water saturation. The effect is most significant for sandstones with high clay content and low residual water saturation and is less significant for clean sandtones or those with high residual water saturation. The experimental results are discussed on the basis of the chemical interaction between water and rocks—capillary stress and relative permeability. It is concluded that water-saturation-induced rock-strength reduction is the most significant factor governing perforation failure and sand production. Although perforation failure is a prerequisite for sand production, the failure does not always lead to sand production.