Sand production from the Sarir field became a major concern for AGOCO at the end of the 1980s when ESPs were introduced to the field. The sanding severely impaired the performance of field, and consequently led to significant economic loss.
AGOCO recognized that it was facing a major challenge in terms of understanding potential sanding risk for Sarir, and that it was necessary to design and implement a sandface completion and sand management strategy for more than 400 wells in the field. It was decided to apply a particular systematical approach, termed as Sand Management Solution (SMS), to properly address the sanding issues it was facing, which involved prediction, prevention, monitoring, and, if required, remediation activities. The first step in the SMS was to obtain a clear understanding of the cause and the mechanism for the sand production. This knowledge was required because attempts to run new completion designs without knowing the cause of the sand and understanding the risks had been proved costly, and would be likely to fail.
To this end, a SMS was implemented in Sarir field. The work started from geomechanical reservoir characterization including geomechanics core laboratory test and mechanical earth model building, sanding prediction and evaluation, and a detailed review of sanding history to understand the severity of the sanding risk and sanding mechanism. Based on this knowledge, sanding management and remedial completion measures were devised that would minimize economic loss caused by sanding and optimize hydrocarbon production.
This paper provides details of implementation of this SMS in the Sarir field, and demonstrates that a systematical approach is required when addressing sanding issues in giant mature fields such as Sarir.
Sanding is a major concern for AGOCO. Sand production can destroy electrical submersible pumps (ESP), erode completion hardware and surface equipment, and block flowlines and trunklines. It can also lead to casing failure or borehole collapse. In addition to the costs associated with lost production, workovers, and the repair of ESPs, surface equipment, and pipelines, operators also have to manage the separation and disposal of the sand produced with the oil.
Sand production from the Sarir field was first recorded in the mid-1970s, when sand fills were discovered during workover operations. At that time the issue was not considered to be a major problem, but that changed at the end of the 1980s when ESPs were introduced across the field. Some of these ESPs, which were installed to sustain production rates, failed as a direct result of sand influx. Since 1984, most wells in Sarir field have been periodically cleaned as a precaution against sanding-related problems.
AGOCO, the field operator, investigated the issue, and in 1992 the first gravel-pack completion was installed in the Well A to prevent sand production. However, sand control measures were not applied across the entire field.
A geomechanics study conducted in 2004 (Sarir Sanding Study Phase I1) examined seven wells in the south eastern part of Sarir. It identified the source and severity of the sand production, linking the problem to the occurrence of thin beds, and proposed new completion solutions to address the issue and optimize production in that part of the field. A Phase II of the study, discussed here, was initiated by Schlumberger in October 2005 to address a further 25 wells located in three areas (GC1, GC2 and GC3) that were deemed to be representative of the whole field. The work covered geomechanical reservoir characterization, review of sanding history, and optimization of completion options. The principal aims of this project were to identify potential sanding risks, propose optimum well completions, and provide a complete SMS for the field.