Investigation On Thermal Stability Of Gravelpack Materials
Authors: Bouhroum A. , Marx C. , Hofling B. 
Published: March 2010

The thermal stability of five gravel pack materials was examined. Experiments were performed under injection and production conditionsto simulate chemical and thermal interactions.

Ottawa sand, Interprop, Carboprop, Zirprop 120 and /26 were sreamflooded in the first case without the presence of oil under borehole conditions (at pressure varying from 8 MPa to 12 MPa and temperatures varying from 280 °C to 320 °C) at an ambient pH value of 9.5. Ottawa sand and Interprop were also tested in the presence of heavy oil.

Microscopical examinations, mass loss as well as grain size analysis showed that lnterprop is extremely, resistant to any dissolution phenomena especially in the presence of an oil phase. After 76 hours steaming, maximal deviations in grain size of 3.4% and with oil of 2.1% were detected whereas the Ottawa sand showed deviations of 15% and 9%, respectively.

Introduction

Thermal methods of oil recovery such as steamflooding and steam stimulation showed good results in heavy oil production(l,2). Especially steam stimulation plays an important role in heavy oil production. This process includes three phases:injection phase: steam is injected into the well;soak phase: steam condensation and heat transfer;production phase: the production of fluids from the heat affected zone.

The application of the steam injection rnay cause serious problems including sand production. The consequence of sand production is the erosion of tubulars, pumps, valves and the obstruction of separators resulting in decrease of production.

One of the popular methods to prevent sand production is the gravel pack technique. In order to achieve effective sand control, the grain size distribution of the filter material must be adapted to that of the reservoir sand.

Under the influence of steam, dissolution of the quartz containing gravel pack material occurs. This leads to a modification of the grain size distribution; consequently it reduces the permeability of the installed filter.

The SiO2 dissolution in water at high temperatures is due to the hydrolysis of Si-O-Si bonds by formation of Si-OH-groups(1,4).

As the first stage, five gravel pack materials have been tested in this work at various temperatures and pressures (temperatures varying between 280 °C and,320 °C, pressure from 8 MPa to 12 MPa) with an experimental set-up having different geometrical dimensions from those of a well. In a second step two of the five gravel pack materials have been studied. One was highly resistant to steam (Interprop), the other being most commonly used in this kind of operation (Ottawa sand). Both have been tested under borehole conditions using Athabasca oil sand as a test bed.

Description of the Test Facilities

To allow appropriate tests [0 be conducted, two test reactors have been developed for subjecting gravel pack materials to simulated injection and production conditions, One experimental set-up (Fig. 2) was used solely for the study of the two chosen gravel types at the same geometrical and flowing borehole conditions. The design of these test facilities is shown in Figures 1 and 2. The essential components of the systems are as follows: