Multi-objective Real-time Optimization Of Drilling Parameters Based On Pareto Optimality

Drilling parameters are one of the most important factors which can affect the penetration rate,the cost and the quality of drilling,a reasonable combination of drilling parameters will no doubt effectively improves the efficiency,decreases the bit wear and the cost.While most traditional optimization methods establish a single-objective model which only takes the cost or rate of penetration into consideration without consideting other factors.However,the working condition tends to be much more complicated as the increment of drilling depth,more comprehensive factors affecting the drilling quality such as the bit life and specific energy are required to be taken into consideration when establishing a drilling model.In addition,the application of intelligent optimization algorithms to effectively solve the real-time optimization has become a key technology in optimizing drilling parameters and intelligent drilling.Therefore,the paper focuses on the multi objective optimization of drilling parameters.Due to the insufficient of the traditional drilling model,a modified drilling model,considering hydraulic factor,drill diameter and formation lithology,was proposed,what's more,a drilling efficiency monitoring model,a drilling status recognition model and a three-objective optimization model with constraints based on the modified drilling model were also established.Furthermore,the building of drilling model in real time was realized by multiple linear regression,and the rationality of the drilling model was verified by a practical example.Improvements focusing on the methods of handling constraints and crowding distance operator were made due to the premature convergence and deficiency of penalty function method in handling constraints in NSGA-?.In order to acquire comparative optimal combination of drilling parameters which are able to meet the demands of different working conditions,Ideal-reference Point theory was put forward to guide the evolution of population,and the application of modified algoritm to multi objective optimization was realized.The performance of modified algorithm based on Ideal-reference Point theory was tested by several optimization problems.The modified algorithm was applied to solve optimization model of drilling parameters which was built based on a coal mine.The results of drilling parameters matching were achieved by choosing different ideal reference point.Furthermore,the effects of different drilling parameters on the quality of drilling were analyzed by comparing the drilling parameters of before and after optimization.To realize the drilling parameters real-time acquisition and storage,a drilling database and a drilling parameters optimization interface were designed based on Matlab.Finally,the real time optimization of drilling parameters was realized based on the research of drilling model and multi objective intelligent optimization algorithms,which provides reference to the research of drilling parameters optimization technique and intelligent drilling equipment.