Filtration of water is critical for maximizing oil and gas production as well as for protecting the environment during oil and gas drilling. To enable the global production of oil and gas that keeps our cars humming, furnaces heating and factories running, producers treat and filter billions of gallons1 of water each day.
Energy production is a huge exercise in particle control – some particulates must be excluded and some particles are deliberately added to the process. With the wrong size particles in completion and fracking fluids, the earth’s underground porous rocks (called “formations”) where hydrocarbons have been formed and stored for millions of years can become plugged, blocking the flow of crude oil or gas. This unfortunate event is called “formation damage,” and sometimes it is irreversible, destroying vast sums in exploration and drilling investment.
What is Fracking?
But formations are sometimes naturally “tight” and not permeable enough to let hydrocarbons out easily – this is especially the case with a type of rock called shale. Fracking, or hydraulic fracturing, employs high pressure fracking fluids (water mixed with a lot of additives) to create fissures in the formations to enable oil and or gas to flow out of the well. Sand or ceramic particles called “proppants”, which are typically hundreds of microns in diameter, are added to fracking fluids to keep these man-made fractures propped open. “Drilling muds” contain particles of calcium carbonate or barite, and form a filter cake in the well bore, thus protecting the production zone.2 Suffice it to say that energy producers care quite a bit about the sizes of particles in fluids and expend quite a bit of effort studying, selecting and controlling particle sizes – both the sizes of particles that are deliberately used (such as proppant and mud), and the particle sizes that must be excluded by filtration.
What is Produced Water?
Not only are fracking fluids pumped into a well, they also pumped back out as “flowback water”. Underground formations where oil and gas reside already have lots of water in them, and this water comes out as “produced water.” In fact, a lot more produced water than oil comes out! These types of water have a lot of chemical and particulate contamination. The handling of this water is governed by regulation. While the severity of environmental regulations can vary by country or state, compliance with these regulations is always challenging and costly. It can cost an energy producer $3 to $12 to treat a barrel of water.3
We mentioned earlier that underground formations can become plugged-up and damaged if the fluids used are not adequately treated and filtered. A producing formation is one which is supplying oil and/or gas. If a producing formation becomes damaged, the flow of oil or gas out of the well slows down or stops. Not only do operators bring hydrocarbons up out of the earth, but very often operators put fluids back into the ground! “Injection wells” are where water or other fluids are pumped into a formation to help push up oil for “secondary recovery” (after all the easier-to-get oil has been brought up during “primary recovery”). “Disposal wells” are where waste water is injected. Those formations must also be protected with filtration, because if an injection or disposal well formation becomes damaged, it cannot accept any more fluids. If there were no place to put waste water, for example, then production operations would have to be halted. After first putting the produced water in a temporary storage pit, producers often spend significant money trucking water long distances so it can be treated off-site.
Besides injection wells or disposal wells, another place to discharge produced water – especially from an offshore oil platform – is “overboard” into the ocean. Protecting oceans from oily residue in produced water is an important but expensive activity. Examples of filters that do this are adsorbent media, liquid-liquid coalescer cartridges, and cross flow membrane systems. Pre-filtration with string wound filters protects oil-water separating equipment and maximizes its efficiency. Particulate filtration can also help to meet environmental standards for suspended solids where those rules exist.
A petroleum drilling operation will constantly process water. The average ratio of produced-water : crude oil is about 4:1!4,5 , A key challenge after separating and recovering coveted crude oil is to remove chemical and particulate contaminants from the remaining water to enable that water to be re-used (for example, to treat another well.) Re-using water for energy production helps to reduce the diversion of precious drinking water to production operations. Some energy companies are trying to eliminate the use of water altogether6, but such activities are still the “exception to the rule.”
Delta Pure String Wound Filters for Produced Water and Waste Water
String wound filters are used in the energy sector in very high volumes throughout the world from North America to the Arabian Peninsula ; and in diverse applications, from “upstream” in drilling and well production, to “downstream” in gas-processing plants and refineries. Delta Pure Filtration manufactures these filters in the United States and ships them around the globe.
Delta Pure Filtration assists energy producers in four ways.
1) Estimated as follows:
30x 10^9 BBL oil produced per year (various sources) http://en.wikipedia.org/wiki/List_of_countries_by_oil_production
3 BBL of water or more per BBL oil http://www.greentechmedia.com/articles/read/produced-water-an-economic-opportunity,
1 BBL = 42 US Gallons
30*10^9 BBL Oil/year x 3 BBL water/1BBL oil x 42 US Gal/1 BBL * 1 year/365 days ≈ 1 x 10^10
2) Engineer Live, “The Importance of Particle Size for Drilling Mud Formulation”, http://www.engineerlive.com/content/18374, as accessed on Jan 2, 2014
3) Greentech Media website, ‘Produced’ Water an Economic Opportunity”, http://www.greentechmedia.com/articles/read/produced-water-an-economic-opportunity, accessed Jan 9, 2014.
4) As presented to AFS on Oct. 15, 2013 by Steffen Schuech, Mann and Hummel, “Development and Application of Ceramic Hollow Fiber Membranes for Solid-Liquid-Separation Processes”. This paper references their source as: Source: Rice Global E&C Forum – January 13th 2012
5) Greentech Media website, “Produced’ Water an Economic Opportunity”, http://www.greentechmedia.com/articles/read/produced-water-an-economic-opportunity, accessed Jan 9, 2014.
6) State Impact, NPR, “Waterless Fracking Makes Headway in Texas, Slowly.” http://stateimpact.npr.org/texas/2013/03/27/waterless-fracking-makes-headway-in-texas-slowly/ , accessed Jan 9, 2014.