Circulation losses are frequently encountered during drilling operations. Therefore, the availability of various sizes and types of lost circulation materials (LCMs) to mitigate these losses are crucial to minimize nonproductive time (NPT) and costs related to the severity of fluid lost to the formation. This paper presents extensive laboratory testing performed to validate the effectiveness of novel LCMs intended for severe-to-total drilling fluid-loss control in overburden and reservoir formations.
Two different families of LCMs were tested in a particle plugging apparatus (PPA) using metallic disks with various slot sizes that simulated different fracture widths under defined pressure and temperature conditions. Initially, low pressures were applied to validate the materials ability to form a plug over the slots. Next, high pressures were applied to validate the deposited plugs ability to maintain their shape, which indicates the fractures plugging effectiveness. Both LCM families easily released the continuous phase at differential pressures of 100 psi and deposited a uniform and firm wall cake that can rapidly seal a wide range of apertures (4 to 7 mm). The LCM plugs deposited on the simulated fractures provided effective pressure containment, withstanding differential pressures as high as 2,000 psi. Additionally, the evaluated materials were visually inspected, and their ability to release water and form a dry wall cake over any high-permeability slot was validated.
Circulation losses are generally countered by mixing various types of LCMs to achieve a defined particle size distribution (PSD), which might only seal one size of fracture. This paper presents laboratory test results, which indicated the two LCM families could seal a wide range of fractures effectively. The first application of the studied LCMs in a naturally fractured ultradeepwater well is also presented.