Thus far we have explored the current technological practices involved in directional drilling; completing a well, including casing, perforating and stimulation; we have discussed enhanced oil recovery, and created an infographic. We have even started exploring some of the financial instruments E&P companies use to reduce the financial risks involved in the capital intensive work of drilling a well – or a pad of wells.
But one big piece of current oilfield technology that is remaining is lift – once the well is drilled and completed, how do we get the hydrocarbons to the surface?
History of Lift
The earliest successful oil wells were drilled into geological formations that were relatively shallow, highly porous and permeable, and had positive pressure from abundant trapped gas to help drive the hydrocarbons to the surface – the classic “gusher”. The physics involved have to do with having a low enough Bottomhole Pressure (BHP) to “lift” the hydrocarbons to the surface. In the case of a gusher, there is enough natural lift to bring the hydrocarbons to the surface; however, in most cases we have to add some “artificial” lift to help them along.
Since folks have been moving water from where it is (a river, maybe, or a well) to where they want it (where the people are, or the crops or livestock) since civilization began, we can start by looking at the technology of moving water around. Early systems for crop irrigation used a shadoof to raise water:
Looks like lifting, right?
After a couple of millennia (c. 200 BC), Archimedes devised the “screw pump”
around the same time Greek inventor and mathematician Ctesibius invented the water organ
Today’s Oil fieldFast forward another couple of millennia into today’s high efficiency Pad Drilling situations with the variable flow rates associated with massive IP/quick decline wells. As always I would like to point out that I am not an Engineer, but if you would like a closer look at the actual equations involved, petrowiki.org has a great technical breakdown of the methods of modern lift.
This is your classic pumpjack oil well pump – the one you see in the fields of East Texas, or in the footage of the Middle East. The above-referenced Petrowiki article says that “Approximately 80% of all US oil wells are stripper wells making less than 10 B/D with some water cut.” The classic beam style pumps (also known as sucker rod pumps) were ideal for the lifecycle in classic conventional E&P and continue to be a dominant method for oilfield lift.
Interestingly, one of the big drawbacks to beam lift, is that the pumps need to run fairly close to perpendicular to the well bore, which becomes complicated in today’s directional applications. Also the most common cause of failure tends to be where the sucker rods have to negotiate bends in the well.
Typically they are maxed out in the 350-400 bbl/day range, but they are very economical to run vs. other types of lift, and as mentioned above can continue to run in part-time stripper well status for years.
Gas Lift uses high pressure gas pumped through downhole valves in order to reduce the hydrostatic pressure and force fluids to the surface.
In wells with lower productivity, they will often employ an “intermittent gas lift” (as opposed to “continuous gas lift”) in order to allow desired hydrocarbons to build up before being forced to the surface.
Injection gas is usually reclaimed at the surface and reused.
Similar to gas lift only using high pressure liquid instead of gas – often a portion of the produced oil from the well itself. Hydraulic lift is often used in deeper wells that require greater lift due to the increased pressure.
Electrical Submersible Pumps (ESP)
A relatively new lift application in the oilfield, ESPs are centrifugal pumps submerged downhole below the level of the reservoir. They use an electrical motor (and a very long power cord) to force hydrocarbons to the surface, and are good for a variety of depths and volumes.
Halliburton’s blog post on Artificial Lift Systems and The 5 P’s has this handy chart for various limits and strengths of the different systems:
Future innovations to watch for in artificial lift
- As efficiency and the environmental concerns about disposal wells continue to effect the industry, there will be more focus on methods of downhole oil/water separation – if we don’t lift the water to the surface, and can re-inject as part of the recovery process, that will reduce concerns on the surface.
- Due to the wildly different flow rates involved in modern unconventional techniques, we will likely see more hybrid solutions brought into the field.
- The geometry and physics of horizontal wells create a lot of opportunity for innovation. Check out this recent piece from American Oil & Gas Reporter on Artificial Lift Optimization for a deeper look at some of the variables involved.
For extra credit, here is a great 30 minute video on sucker rod pumping:
What do you think? Leave a comment below.
Latest posts by Eric Roach (see all)
- The STACK, The SCOOP and Oklahoma Oil & Gas - April 11, 2017
- BP’s Road Forward: US Onshore Activity - August 4, 2016
- Midland Basin Update: The Permian’s Older and Wiser Half - July 28, 2016