Prevent screen and completion damage.
An operator’s oil wells in the Caspian Sea were experiencing excessive sand production from intervals of unconsolidated sandstone that ranged in thickness from about 15 m [49 ft] to several tens of meters. Shortage of available rigs and challenging procedures for importing equipment prevented widespread use of cased hole gravel packing. Stand-alone screens were deployed instead for time and cost efficiency, but high flow rates and the abrasive sand eroded them rapidly. Plugged perforations and accumulated fill were common issues.
Most wells had to be choked back multiple times over a 6-month period and required sand cleanouts every 3–6 months. In addition to reduced or lost production, wellbore equipment failures, sand separation and disposal in the environmentally sensitive region, and the periodic CT-assisted cleanout operations were having a negative impact on project economics.
One well had an initial production rate of 300–400 bbl/d with about 1% sand on surface. When sand production became excessive, oil flow was restricted and CT cleanouts were conducted periodically. To address these challenges, Schlumberger suggested treating the well with field-proven SandAid sand conglomeration technology, a patented chemical solution that increases the attraction between particles. It traps formation sand and fines while retaining high levels of permeability to maximize sand-free flow rates and increase production.
Designing the treatment for the well required extensive laboratory testing to optimize sand agglomeration and ensure compatibility with formation crude. X-ray diffraction and analysis of produced sand samples assisted chemical additive selection, and the treatment was modeled using Kinetix Matrix matrix stimulation design software to ensure adequate penetration into the rock matrix. Engineers devised a schedule to treat each of the four perforation intervals with several cycles of preflush and main fluid for maximum success. Mobilizing a rig was not necessary.
The well was cleaned out using CT, and a step-rate test was performed to determine formation fracture pressure and optimize treatment injection rate. After bullheading the treatment into the well, software simulation was run to ensure that adequate reservoir contact and zone coverage had been achieved. Subsequently, the well was shut in for a day to enable the migrating sand to agglomerate. The shut-in period was extended because of delayed availability of a jet pump to restart flow. Because the reservoir in the drainage radius of the well was already depleted, the well could not be started with natural flow.
When production resumed, after formation cleanup and well testing the flow rate gradually increased to >600 bbl/d with zero sand production. This flow was maintained for nearly one year with no sand on surface, improving profitability. SandAid technology is now under consideration for application in other wells in this field.
More information can be found in SPE-204714, which will be available after presentation at the SPE Middle East Oil & Gas Show and Conference in 2022.
Proprietary chemical sand conglomeration technology stopped stubborn sand production from an unconsolidated formation, avoiding the need to gravel pack, sidetrack, choke back production, or shut down the well every few months for cleanout.