Most oil reservoirs contain some form of gas within the oil/fluid solution that requires various types of equipment to be used at the well site. This equipment can include separators, pumps and compressors. In some cases, two flow lines are required: one for the pumped liquid and one for the compressed gas—requiring double the equipment.
Roughly six out of every 10 wells are multiphase with variation in the fluid makeup, rheology and viscosity. Along with this variation, small solid particles such as drilling cuttings or paraffin are commonly found in the mixture. This necessitates local separation at each well site, which means there is a large footprint of equipment infrastructure at or near each well site.
Along with the complex infrastructure, something must be done with the various phases (solids, oil, water and gas) once separated. Traditionally, each phase of product is handled individually after local separation, but this is costly and requires a large footprint. Because of these challenges, companies have investigated the advantages of multiphase pumping, which is the transfer of fluid containing any combination of gas, liquid and solids from the well site or satellite location to a central processing facility.
One manufacturer spoke with end users and researched ways to design a multiphase pump system that would meet end user demands and provide a pump that made gas, liquid and solid separation unnecessary near the wellhead, allowing mixtures to be pumped to a single facility for processing.
The resulting research yielded the development of a multiphase transfer system that handles every phase without the need for multiple pumps as with the traditional method. This system is based on field-proven progressing cavity pump technology that is designed to handle every phase with its advanced technology and design.
The system offers a highly effective pumping solution for the difficult and fluctuating conditions that are often encountered in multiphase fluid flow. The system also provides pump controls that help maintain constant pressure and allow the user to adjust pump speed depending on the well flow conditions.
Installing this multiphase pump allows users to decrease the wellhead pressure, creating incremental flow from the well. It performs compression and pumping to handle the different phases. The system is installed on the surface so that all phases from the well are fed directly to the pump, eliminating the need for local separation and transfer of fluid into a treater system where solids are removed and pumped to another facility. Eliminating tanks, separators and other equipment can minimize overall footprint and equipment costs.
This system simplifies the production process. It is specifically designed for difficult pumping applications and easily handles the different fluctuations, all three phases and other substances without the need for separators or compression of gases.
It is then able to pump the fluid down a single line and into a central processing facility. The pump design enables it to pump the oil and water combination without emulsifying the mixture, which other pumps are not able to do. These benefits enable users to reduce capital expenditures, promote environmental sustainability and provide flow assurance.
In the Field
Operators using the multiphase transfer system have seen direct cost savings in reducing the amount of separation and processing equipment they require on-site. The system was recently used in Canada, where the user had a large well field with only one central processing facility. The field included several dominant wells where excessive flowline pressure caused wells to shut down. When the multiphase pump was implemented, the user had a production increase of 500 barrels of oil per day (BOPD) and a payback of less than six months.
Another study was conducted in Canada in a remote location in extreme northern British Columbia. Access to this field was limited because of the harsh weather and road conditions. The operator had 62 wells that were fed to the satellite processing facility. Equipment reliability was critical in this project because of the challenging location. After installing and using the multiphase transfer system, the operator saw an increase in oil production of 40 cubic meters per day and the wellhead pressure reduced to 10 pounds per square inch. Overall, the operator had a payback period of just eight months at $20 per barrel of oil.
An end user in North Africa also began using the system after noticing some aging wells that were still capable of producing oil but needed an alternative solution to gas flaring. A pilot project was implemented with two pumps, and the end user saw a production increase of 2,500 BOPD with a payback of less than five months. The success of this well led the user to install the pump system on 15 additional wells.
This multiphase pump has increased production rates and has several environmental benefits. It eliminates the need to flare gas at the well site, eliminates local water storage and disposal, and exhibits a small environmental footprint. Over time, multiphase pumping has evolved to become a “best practice” in some areas. Companies are now looking at it to solve a wide range of operational challenges. With more than 160 pumps in operation, producers have seen how these pumps improve production rates, eliminate emissions and reduce capital costs.