No abstract

In the current oil fields in China, the horizontal well technology with a long horizontal interval has gradually become the core technology to develop conventional oil and gas reservoirs, and the accurate determination of the drag and torque of the drill string is the key. However, the determination of the friction coefficient is affected by many factors, and it is difficult to describe it clearly by mathematical formulas. According to the characteristics of friction factors, the method of calculating the friction coefficient of drill string is studied, and a prediction model of friction coefficient based on BP algorithm is established. Based on the predicted friction coefficient, the calculation method of drag and torque is analyzed, and a drag and torque prediction model based on BP algorithm is established. The experimental results show that the use of BP neural network can accurately predict the friction coefficient and torque, and the prediction of the friction coefficient can characterize the risk of sticking of the drill string to a certain extent, which facilitates the adjustment of drilling parameters on site to improve the safety during drilling.

A functional pre-anodized carbon paste electrode (PACPE) was prepared by 35 successive cycles of scans between 1.0V-1.8V in 0.2 mol L-1 NaOH solution. The electrode reaction mechanism of trimetazidine hydrochloride (TMZ) was carefully studied by CV method and was determined as a twoelectron/two-proton process, which is put forward for the first time. Experiment showed that the electrostatic attraction between the protonated TMZ and the negatively charged PACPE surface, both were affected by pH, was the dominant factor influencing the adsorption and the peak current. The PACPE exhibited excellent electrocatalytic effects towards the oxidation of TMZ. In the optimum conditions, the oxidation peak current was linear with TMZ concentration in the range of 5.0×10-7-5.0×10-5 M (r=0.998), and the detection limit was estimated to be about 1.5×10-7 M. This method can be successfully applied to the determination of TMZ in pharmaceutical formulation.