Optimization of plug utilized in lost circulation treatment while drilling

摘要

The major problem of oil wells drilling is circulation lost that can occur near weak formations and before well cementing. Conventional methods such as lost circulation material pills, cement plugs and dual injection were used to combat different types of massive mud loss in spite of their small success rate and high cost and risk. A different circulation treatment has been introduced to optimize plugging of loss zones by minimizing cost and time. It consists of combining InstanSeal (seal formation instantly) and cement to improve the mechanical performance of the system. InstanSeal-cement plugging fluid is a loose invert emulsion (water-in- oil) that gels rapidly in normal drilling operations after passing through the drill bit nozzles resulting in a rigid direct emulsion (oil - in- water) which will be squeezed and penetrated into weak formations to seal it. It is the only gelling system that uses mechanical means as a trigger mechanism. The present work aims to optimize the emulsion mechanism, the composition effect and the InstanSeal-cement as follows: (i) Introduce the InstanSeal-cement as an approach to cure massive losses where conventional methods fail. (ii) Analyze the evolution of InstanSeal-cement fluid by changing each product concentration. (iii) Find the proper emulsion of each kind of losses. (iv) Optimize the system according to the equipment taking into account the mixing energy. (v) Find the most effective formulation using mathematic models. (vi) The laboratory pre-checks will be taken as helping data to minimize the failure risk. After the success results obtained from the yard test, the InstanSeal-cement proved that it is competent to cure massive losses by improving the success rate (80%). This economic success can be matched by reducing risks, achieving excellent results and decreasing drilling time through a critical section.