Design And Research On Cylindrical Capacitance Sensor Applied In Water-cut Logging In A Horizontal Well

Horizontal well, which rapidly developed at the end of the 20th century in China, can improve oil well production and the efficiency of the development. Usually a horizontal well cost as 2.5 to 3.5 times as a vertical well with the same depth, but oil production of the former can increase 1.4 to 9.2 times, therefore the horizontal well technology has been treated seriously by oil industry generally. Drilling technology of horizontal well has become increasingly perfect mature, but due to difficulties of the logging equipment transportation, and the complicated flow patterns, production logging technology of horizontal wells developed slowly. Many oil fields have already successfully developed horizontal wells, which have achieved good economic benefits, but long-term development leads to instability of well production, and water-cut of some horizontal wells rise rapidly as soon as the well starting to produce water, which consequently make oil production decreased significantly. To solve these problems, geological researchers must understand the underground condition to determine its better reform plan, which made even more urgent requirements to production logging. At present in China, more and more researches on horizontal well technology have been carried out.This subject is funded by the state 863 projects(2007AA06Z231), against domestic low-yield horizontal wells, proposed a novel capacitance sensor which can be used in measuring the production frofile water-cut. The sensor with cylindrical structure does not impede fluid flow and does not destroy flow field distribution. It has high reliability and strongly targeted performance which is applicable to the water-cut measurement of stratified flow, and therefore it has good application prospects.In this paper, the principle structure of cylindrical capacitance sensor has been discribed, the measurement principle of the sensor was analyzed, and the mathematical model of the sensor was established. Electric field of two-dimensional has been simulated through ANSYS software, and mechanical drawings of the sensor have been designed for experiment. Indoor static experiments have been carried out, and through analyzing the experimental results, the factors which can impact the sensor response were found out. "Hight" method principle experiment results show that using this method logging water-cut of low-flow horizontal well has good repeatability and consistency, verified the theory. The purpose of stain, salinity and temperature response experiments is to determine the impact of stain, salinity and temperature to the sensor response, and to point the mechanism of the impacts; the circuits were designed and the prototypes were assemblied, on Daqing multiphase dynamic simulation wells mechanical experiments are conducted and the charts are calibrated, the range of the flowrate 5 ~ 30 m3/day, water-cut 0 -100%. This paper has provided references for the spot application, at the same time it makes a preliminary analysis for the level of wells on the flow of fluid conducted; finally, this paper concluse the whole subject, made suggestions and prospects.