The drillers knowledgebase is a questions and answers area for the drilling community to learn and share knowledge and experience. This particular question has been moved from the old drillers.com website and the answers are displayed in the body of the article. If you have a further comment then feel free to add it in the comments section at the bottom of the page. If you want to ask a new question then there is a question entry box further down.
What are the drilling problems caused by gumbo/swelling shale? And how?
e.g. swelling shale can result in stuck pipe.
(Question asked by Sher)
Hi Sher, Some shale types react strongly with water based mud. This causes the shale to hydrate and swell; shale cuttings in the well become sticky so clump together, or can stick to the steel drillstring downhole, closing up the annulus and causing swabbing and stuck pipe.
On the surface, sticky hydrated shales can plug up the shale shaker screens, causing loss of mud over the shakers. The solutions include getting water based mud chemistry correct to prevent shale hydration or to use oil based mud.
(Answered by Fiona Webster)
The characteristic that makes shale most troublesome to drill is its water sensitivity, due in part to its clay content and the ionic composition of the clay. Shale absorption to water usually leads to dispersion and swelling. Dispersion occurs when the shale subdivides into small particles and enters the drilling mud as drill solids. Swelling occurs due to an increase in size of the silicate minerals increasing the clay structure (layers of clay penetrated by water) leading to hole destabilization : caving or sloughing shale.
In order to avoid such problems, the following measures should be taken in the sections containing shales * Change of the chemical composition of the mud by adding potassium for instance. This will reduce the chemical attraction between shale and water or by using an oil-based mud. MI-SWACO proposes special mud type ULTRADRILL * Minimize the time for which the section containing the shale uncased.
Answered by Mohamed BOUMEZRAG
Submit your question to be published on drillers.com
(Or scroll down to add an answer or read further comments and answers)
PS: If you have a very technical question, you ought to head over to our drilling specialists nirvana, my-spread.com. It is a free to join forum with around 2000 members including some of the most knowledgeable engineers and geologists in the world. Most, if not all major oil and service companies are represented there. Of course, you are more than welcome to post your question on drillers.com AND my-spread.com to have the maximum opportunity for the response that you are looking for.