Sand production is one of the major technico-economical constraints that reservoir, completion and production engineers have to take into account in order to optimize the exploitation of a reservoir in poorly consolidated sandstones.
The options are essentially of two kinds:
either the installation of a sand control technique in case of unmanageable quantities of sand, which will in turn ensure the safety of operations but also often penalize the well productivity;
or the acceptance of a tolerable amount of sand production, which will enhance strongly the productivity of the wells but may require a careful planning in terms of possible well choke-backs, periodical cleanings of the bottom hole, selective perforations, proper dimensioning of the surface production facilities, reservoir pressure maintenance, etc.
An optimum technico-economical choice therefore requires to know, since the beginning of the development of a new field, if and when sand production will start and which kind of operative problems it will cause. With this important priority in mind, Agip has recently completed an extensive research project, which allowed two major achievements:
a deeper understanding of the mechanisms governing the physical process of sand production;
and consequently the development of a field-validated methodology, which allows an accurate prediction of the critical conditions at which sand production starts. Since then, this methodology has been applied successfully on more than ten fields around the world.
This paper then will:
summarize the findings of the research project;
define the recommended best practices in order to perform an effective and accurate prediction analysis;
show the strategy that is currently adopted in order to define reliable criteria to estimate the operative risks linked with the production of sand.
All three points are illustrated by examples drawn from the field experience gathered by Agip. Special emphasis is put on operational aspects such as the rig-site tests capable of measuring the quantity of produced sand, the dimensioning of surface facilities, the use of solids transport models, field validation and calibration of pipe erosion models, etc.
An effective strategy allowing to manage the sand production risk has a strong economic impact during the exploitation of reservoirs in poorly consolidated sandstones, as it allows to select the best technical choices in order to optimize the production performances.
In fact, on the one hand, there is the fear either of serious operative problems associated with the onset of sand production (erosion of the downhole and/or well-head lines and chokes, plugging of perforations, filling of the separators, etc.) or, in wells already producing sand, of an increase in the sand rate due, for instance, to water breakthrough.
On the other hand, there are the economic considerations related to the productivity reduction that may occur as a consequence of the application of a sand control technique (frac-packs, gravel packs, pre-packed screens, etc.) and to the intrinsic costs of such jobs.
This paper summarizes Agip's own strategy, which allows:
to predict reliably the operative critical conditions for the onset of sand production;
in case of recognized risk, to estimate whether sand production can be considered operatively tolerable;
to identify whether technical solutions can be adopted in order to make sand production tolerable.