Gravel Packing in Poorly Lithified Reservoirs: Laboratory Systems Approach to Aid Decision-Making Strategies

Abstract

ABSTRACT Economic and effective recovery of hydrocarbons from poorly lithified reservoirs, particularly in offshore regions, can be adversely affected either by failing to gravel pack or by unnecessarily gravel packing a well. The decision to gravel pack can be aided by a laboratory systems approach specifically designed to determine reservoir susceptibility to sand production. This approach intergrates engineering and geological tests to determine the effects of anticipated production rates on reservoir sand production at variable WOR. These tests include: Petrographic evaluations of reservoir sanding potential including grain size and shape, uniformity coefficient and degree of lithification. Wettability determination for fines, sand and gravel, to ascertain fluid phases in which fines/sand particles would be transported. Measurement of two-phase critical velocity, as a function of WOR, at reservoir conditions to establish maximum production rates before fines and sand will be fluidized. Acoustical measurement (vp, vs) to calculate critical drawdown pressures for shear failure in poorly lithified rocks at reservoir conditions. If this system analysis indicates a gravel pack is needed to alleviate anticipated sanding problems, gravel grain size and gravel pack permeability can be determined to calculate expected gross production rate. Specific examples are presented to document the efficiency of laboratory procedures in aiding the decision to gravel pack.