Session: 11-02-03 Well Drilling Fluids and Hydraulics -3

Paper Number: 79502

79502 - Comparison of Lost Circulation Material Sealing Effectiveness in Water-Based and Oil-Based Drilling Fluids and Under Conditions of Mechanical Shear and High Differential Pressures 

Lost circulation is a critical factor which may reduce drilling efficiency, increase cost and increase the risk of well collapse. Oil-based drilling fluids are often considered as superior to water-based drilling fluids with regards to obtaining a low fluid loss and achieving high rates of penetration. Water-based drilling fluids are in contrast often preferred due to a lower cost if the risk of large or total losses of drilling fluid is expected.

A study was conducted to assess the performance of granular and fibrous lost circulation materials as preventative treatments and in remedial treatment of lost circulation in water-based and oil-based drilling fluids. For the preventative treatments, a factor which introduced increased mechanical wear on the particles were added to the hot-rolling process, to identify signs of deterioration of performance of certain materials.

The study of remedial treatments of lost circulation were conducted on slotted discs with apertures of 750 µm and up to 5 mm, and with differential pressured of up to 34.5 MPa (5000psi).

In order to compare the sealing pressures of the different tests, a statistical analysis was introduced to differentiate between the peak holding pressures and the sustainable holding pressures of the various material and fluids combinations.

The material degradation studies showed that CaCO₃ based lost circulation materials rapidly experienced significant particle degradation after exposure to fluid shear of mechanical degradation and that this considerably reduced the sealing performance of the materials. Also, synthetic graphite-based products showed clear signs in particle size degradation and significant reduction in sealing performance. Fibre-based products showed superior resistance towards mechanical wear and only small changes in sealing performance.

When comparing water-based and oil-based fluids, it was clear that granular lost circulation materials showed considerably lower sealing efficiency in oil-based drilling fluid compared to water-based drilling fluids. In contrast, fibre-based materials showed similar sealing performance in oil-based fluids and water-based fluids.

Presenting Author: Karl Ronny Klungtvedt EMC

Authors:

Karl Ronny Klungtvedt EMC
Arild Saasen University of Stavanger