Holistic Approach Toward's the Deployment of Various Lost Circulation Control Materials Yields Cementing Rewards in the Caspian Region

Abstract

Abstract This paper chronicles cases histories both on land and offshore environments that demonstrates the efficacy of different lost circulation systems and products that are used either individually or cooperatively to mitigate losses ranging from severe to partial. The application of different systems and products for losses stemming from highly permeable formations, weak formations, and natural fractures are discussed. Simulated software results and laboratory test data are also presented, providing quantitative and qualitative evidence. The paper covers a review of cement jobs undertaken over the past 2 – ½ years commencing in 2013. These jobs cover land operation in Kazakhstan as well as operations in the Caspian Sea offshore Azerbaijan. The severity of the losses encountered ranged from anticipated to upwards of 90% prior to cementing. Various lost-circulation control techniques are analyzed, ranging from the use of novel cement spacers, inclusion of fiber products within the cement slurry, pumping alternative non-portlandite cement materials, or combining those technologies. In some cases, post-job hydraulic analysis of the downhole equivalent circulating densities encountered will be used to validate the success of the techniques. Laboratory data from tests attempting to simulate the downhole fractures and sealing properties will also be included, providing quantitative and qualitative evidence of the need for further investigation in the application of various fibrous materials. Over the course of the jobs, it became quite conclusive: ➢ The use of novel cement spacers including additional fiber /solids can reduce losses in circulation by 100% or in the case where losses were anticipated while cementing, results with no losses at all and cementing objectives being achieved. This application covers cases where there were losses upwards of 20 bbls per hour before commencing the cementing operations. ➢ Lost-circulation plugs using a non-portlandite system can successfully stop losses while drilling, allowing for subsequent RIH and primary cementing operations. ➢ The Portland cement is an excellent lost-circulation control material by itself. However, the results will show cases where microfractures are induced during the primary cementing operations due to relatively low fracture gradients. The use of fiber elements within the cement slurry will assist in sealing the micro-fractures, preventing catastrophic losses during the cement job. Lab tests simulating micro-fractures up to 6 mm demonstrate that they can be sealed off by adding fiber and solid materials to the cement slurry. ➢ Proper research of historical files and jobs conducted within an area helps the drilling team assess the potential risks and pre-plan to mitigate such risks. Combinations of the various loss circulation control techniques can then be factored into the design. One case history documents this approach, leading to the successful achievement of the cementing objectives. ➢ The holistic, data-driven approach is an ideal way of selecting lost-circulation materials and should have applicability as a best-practices approach around the world. The holistic, data-driven approach is an ideal way of selecting lost-circulation materials and should have applicability as a best-practices approach around the world.