Quantification of sand production induced improvement in productivity index

Abstract

Centrifuge physical model tests were performed to study the mode of failure during sand production and its concomitant impact on the productivity index. The tests simulated seepage-induced failure around a multiperforated vertical well. Results indicate that in the presence of a competent cap rock (1) sand production results in the formation of a truncated cone-shaped enlarged cavity; (2) surface subsidence of the reservoir due to loss of sand mass may result in the opening of flow channels under the cap rock; (3) for a given applied head difference, sand production ceases once the enlarged cavity reduces the pressure gradient to subcritical levels; (4) the flow becomes diverted towards the upper perforations where the cavity radius is largest; and (5) the flow rate increase varies between 5 and 10 times depending on whether the mode and volume of sanding is sufficient to result in the formation of flow channels. The study performed shows that (1) the location of perforations affects the mode and magnitude of sand production; and (2) long-term productivity can be improved through managed sand production. The presence of a competent cap rock is the key to achieving substantial increases (an order of magnitude) in productivity via sanding.Key words: centrifuge test, sand production, well-bore completion, subsidence, oil sand, flow improvement.

Numerical simulation of the liquid-induced erosion in a weakly bonded sand assembly

“…In such a process, three stages can be identified: (i) failure of formation rock, involving the loss of mechanical integrity of rocks surrounding a cavity; (ii) mobilization of sand particles from the failed formation rock, involving the separation of sand particles from the formation due to hydrodynamic force [5]; and (iii) transportation of sand particles by fluid. Such sand production processes have been studied either experimentally [5][6][7][8][9] or mathematically [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] in the past decades. For an unconsolidated or weakly bonded particle assembly, sand erosion by flowing liquid plays an important role.…”

“…The common feature for all the continuum-based/empirical models is the establishment of the conditions under which sand failure will occur, and the use of some parameters which are calibrated with laboratory and/or field observations to predict the sand erosion rate. Various models for prediction of sand erosion rate have been developed [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. For example, Papamichos and Malmanger [21] developed the volumetric sand production model where it is assumed that sand is released through an erosion process.…”