The thermal stability of five gravel pack materials was examined.
Experiments were performed under injection and production conditions in order to simulate chemical and thermal interactions. Ottawa sand, Interprop, Carboprop, Zirprop 120 and 126 were steam flooded in the first case without presence of oil under borehole conditions (at pressure varying from 8.0 to 12 MFa and temperatures varying from 280 to 320 °C) at a pH value of about 9.5. Ottawa sand and Interprop were also tested with presence of heavy oil.
Microscopical examinations, mass loss as well as grain size analysis showed that Interprop is extremely resistent to any dissolution phenomena especially under presence of an oil 'phase in the steam. After 76 h 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.
Thermal methods of oil recovery such as steam flooding 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.
waiting phase: steam condensation and heat transfer.
production phase: the production of fluids from the heat affected zone.
The application of the steam injection may cause serious problems including sand production. The consequence of sand production is the erosion of tubular, pumps, valves and the Obstruction of separators beside decrease of production rate.
One of the popular methods to prevent sand production is the gravel pack technique. In order to achieve an effective sand control the grain size distribution of the filter material must be adopted to that of the reservoir sand.
Under the influence of steam a dissolution of the quartz containing gravel 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 under formation of Si-OH group3,4.
At the first stage five gravel pack materials have been tested in this work, at various temperatures and pressures (temperature varying between 280 and 320 °C, pressure from 8.0 to 12.0 MPa).
In a second step, two from the five gravel materials have been particularly studied. One highly resistent to steam (Interprop), the other being the most used one in this kind of operations (Ottawn sand). Both have been tested under borehole conditions in the presence of an Athabasca oil sand representing the reservoir of the test assembly.
In order to allow appropriate test to be conducted, two test apparatures have been developed for subjecting gravel pack materials to simulated injection and production conditions. One experimental set-up was used for the particular study of the two choosen gravel types.
The design of these test facilities is shown in figure 1 and 2. The essential components of the systems are as follows:
