World Library  
Flag as Inappropriate
Email this Article

Lost Circulation

Article Id: WHEBN0019075363
Reproduction Date:

Title: Lost Circulation  
Author: World Heritage Encyclopedia
Language: English
Subject: Drilling fluid, Geosteering, Surgutneftegas, TyumenNIIgiprogas, Artificial lift
Publisher: World Heritage Encyclopedia

Lost Circulation

In oil or gas well drilling, lost circulation occurs when drilling fluid, known commonly as "mud", flows into one or more geological formations instead of returning up the annulus. Lost circulation can be a serious problem during the drilling of an oil well or gas well.


The consequences of lost circulation can be as little as the loss of a few dollars of drilling fluid, or as disastrous as a blowout and loss of life, so close monitoring of tanks, pits, and flow from the well, to quickly assess and control lost circulation, is taught and practiced. If the amount of fluid in the wellbore drops due to lost circulation (or any other reason), hydrostatic pressure is reduced, which can allow a gas or fluid which is under a higher pressure than the reduced hydrostatic pressure to flow into the wellbore.

Another consequence of lost circulation is dry drilling. Dry drilling occurs when fluid is completely lost from the well bore without actual drilling coming to a stop. The effects of dry drilling range from as minor as destroying a bit to as serious as major damage to the wellbore requiring a new well to be drilled. Dry drilling can also cause severe damage to the drill string, including snapping the pipe, and the drilling rig itself.


Lost circulation can be divided into the following categories:

Seepage: up to 10 barrels per hour

Partial: 10 - 50 barrels per hour

Severe: >50 barrels per hour

Total: 100%


Although preferred, stopping lost circulation completely is not always possible or required. Controlled losses allow drilling to continue while keeping the wellbore full, preventing an influx of gas or fluid into the wellbore, known as a" kick", which can lead to a blowout.

A number of options are available when lost circulation occurs, depending on the severity.

  • Minor losses may be controlled by increasing the viscosity of the fluid with bentonite and/or polymers, or with the addition of other additives, which typically includes organic plant particles.
  • Severe losses will require increasing the viscosity of the fluid with bentonite and/or polymers and the addition of other additives, which typically includes organic plant particles.

Total losses can be regained through conventional use of increased viscosity and additives, or through use of unconventional methods such as pumping of large organic particles (like kenaf), paper and large mica flakes with a high viscosity fluid. If total losses occur and circulation cannot be regained, several options are available, depending on the operational requirements and depth being drilled in relation to desired production geological zones. Continuing drilling while pumping drilling fluid is one option, though continued drilling while pumping water is less costly and more often used. Sometimes the cuttings from continued drilling will aid in reducing leaks or stop losses altogether. A third option is to cement the zone where the losses occurred, and to drill through the cement and continue drilling the well. This third option is very often the most cost effective if severe losses occur, as lost circulation sometimes cannot be controlled with other methods.


  • There are many different types and particle sizes used as loss circulation materials (LCM). Products are both organic and synthetic man made materials. Examples of loss circulation materials are: calcium carbonates, crushed mica, cellulosic plant particles, graphite and dolomites. Plant organic particles are usually micronized to go through a 230 mesh screen. Plant materials that have been used are kenaf, walnut hulls, peanut hulls, coconut coir and a number of others.
  • Polymers are also sometimes used to increase the viscosity. Though these are more costly, they are more compatible with several types of fluid systems.
  • There is a great variety of additives which physically plug or seal the losses, including sawdust, flaked cellophane, and crushed or ground gypsum.
  • Other common and cheaper additives are shredded newspaper and cotton seed hulls. Cotton seed hulls are less preferred as they may cause wear to pump swabs and springs. Both of these are generally only used when either fresh or brine water is being used for the drilling fluid.
  • When drilling in salt formations, brine water is typically used, as it does not as readily dissolve salt, preventing the formation of washouts. Washouts not only contribute to loss of circulation, but can jeopardize the integrity of the wellbore itself.

Additive considerations

Several factors are considered in what additives are used:

  • Hole size currently being drilled.
  • Drilling fluid in use. The additives must be compatible.
  • Depth of the well in regards to geological stability.
  • Depth of well in relation to the desired production zones. Plugging a production zone is not a desired outcome.
  • Drill bit nozzles sizes. If the additive(s) will not go through the drill bit, they
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.