The development, validation, and large-scale deployment of online solids management systems is saving operators money by releasing flowback equipment sooner, minimizing equipment damage due to solids carry-over, and reducing the need for shutdowns and confined space entry cleanout operations.

The Sand Challenge

Oil and gas wells seldom produce a nice clean stream of hydrocarbons. Process equipment runs smoothly until a fourth phase comes along: solids.

In conventional reservoirs, produced solids originate from either unconsolidated formations or precipitates coming out of solution. In shale plays, they are mostly back-produced proppant from hydraulic fracture stimulation—an inevitable consequence of the stimulation process, which can only be partially mitigated using temporary flowback equipment.

Each mechanism can lead to significant solids accumulating in separators, FWKOs, heater-treaters, and tanks and, if not addressed there, making their way into downstream equipment.

The consequences of unmitigated solids accumulation and carry-over include reduced separation efficiency, suboptimal oil and water quality, damage to valves, pumps, and heaters, and pipe erosion.

Solids production from a given well or pad can also be highly erratic, causing a sudden increase in solids accumulation that may go undetected between periodic measurements.

It is therefore essential to regularly remove solids from process equipment to optimize performance, minimize maintenance costs, and mitigate the risk of leaks and environmental damage.

Hose and a Shovel

Traditional solids removal requires taking vessels and tanks out of service for depressurization, emptying, and cleaning.

Cleaning larger equipment requires a confined space entry operation, sending a human inside to shovel out the solids. This is dangerous work, often requiring a hazmat suit and breathing apparatus. Sadly, serious accidents are not uncommon.

Cleanout operations are also costly. In addition to service fees, the operator must account for production deferment during the cleanout and while ramping wells back up to full production.

This drives operators to delay cleanouts, which can lead to solids carry-over into downstream equipment. Ensuing valve erosion can lead to oil and gas entering the water leg, creating a hazard in the tank battery and damaging other equipment.

Online Solids Management

Systems using water jets to stir up sand for removal have been tried for decades but found to be relatively ineffective. The breakthrough came when fit-for-purpose materials were combined with vortex fluidizing technology.

Water is pumped into the system through an available nozzle and via distribution hubs to vortex fluidizing units (VFUs) arranged along the bottom of the vessel. The VFUs swirl surrounding solids into a slurry, which is then sucked out of the vessel via a discharge line to a vacuum truck or storage tank.

The system is known as the Octopus™ because each distribution hub typically connects to four fluidizing units, each with a clean water hose and a slurry return hose (so, eight “legs” in total).

For benign operating temperatures and pressures, the system is constructed from high-density polyethylene (HDPE) components, the flexibility of which makes the equipment highly adaptable to different vessel sizes and configurations. For higher temperatures, stainless steel components and braided steel hoses are used to retain system flexibility while making it resistant to the operating environment.

Installation can be performed during vessel fabrication or during a shutdown and clean out of an existing vessel. Multiple Octopi are installed in larger vessels and tanks to ensure effective solids removal.

While permanent pipework and pumping equipment are typically installed to support the regular cleanout of central production vessels, trailer mounted equipment can be used to periodically activate the system in a well pad separator or tank, using a water truck and vacuum truck.

The true beauty of this approach is that it can be activated while the vessel remains in service, avoiding production deferment and obviating the need for human intervention.

A Flourishing Consortium of Octopi

Over 180 Octopus units have been deployed across the Permian Basin and Western Canada, in separators ranging from 60” to 120” in diameter and tanks of many sizes. The system’s effectiveness has been demonstrated using before and after IR imaging.

The cost of each cleanout is reduced by more than two thirds and production deferment is avoided entirely. This usually pays for the Octopus hardware and installation with the first cleanout cycle. The ROI is multiplied when an operator gains confidence to release post-frac flowback equipment sooner than normal.

And, while these savings are a welcome sight for cost-sensitive operators, the HSE benefits of eliminating confined space entry cleanouts must not be overlooked, as well as reduced maintenance and spill remediation costs thanks to regular and more effective online cleanouts.

The Octopus is as close to a “no-brainer” as you’re going to find for most onshore operations, with only a few limitations:

• The horizontal footprint of the vessel must be large enough to accommodate the solids management system. Very small separators and some vertical vessels are not candidates for this technology.
• Retrofits either require existing drains and spare nozzles or the cutting, welding, and certification of new vessel penetrations.
• When a flowback spread is released before solids production has been minimized, the wellhead choke and associated pipework are exposed to elevated solids. Additional monitoring and maintenance should be factored into the cost-benefit analysis.

Conclusions

A superior solution for online solids management has been developed using vortex fluidizing units to effectively remove solids while the vessel or tank remains in service. This avoids the need for process interruption and hazardous cleanout operations while greatly reducing the risk of downstream equipment damage.

The system often pays for itself within weeks, and subsequent cleanout operations are significantly cheaper than traditional approaches that require shutting down and draining the vessel.

With more than 180 systems in operation, operators are encouraged to evaluate online solids management for inclusion in their basis for design of new production facilities and for retrofitting to existing vessels and tanks.

Wolf Process Technology

Wolf Process Technology produces safe, affordable, solids management solutions that protect people, processes, and the environment while ensuring equipment uptime. Our flagship product, the Octopus™, removes solids from vessels and tanks without taking them out of service.