Modified Study On Experimental Technique For Lost Circulation Evaluation

In the drilling process lost circulation is one of the most complicate problems. In recent years, the technology of leak protection and plugging has developed greatly. New technology of leak protection and plugging materials is emerging continuously. However, the limited selfadaption of plugging materials and the lack of scientific evaluation of experimental techniques have led to lack of specific pertinence on evaluation of plugging materials, the unsatisfactory on-site result, and the hanging problem of lost circulation. Due to the absence of scientific evaluation technology, practical evaluation methods of the plugging materials have not been formed. The leakage mechanism, leak protection, and the mechanism of plugging materials lack understanding. Therefore, the evaluation technology is urgently needed to establish or improve.In this paper, through literature research on the evaluation technology of plugging experiment at home and abroad and based on current problems, the interior plugging experimental apparatus has been improved, and the corresponding experimental method for evaluating the indoor plugging experiment has been established. The improvement of experimental apparatus mainly includes:①the design of spiral agitator on dynamic means;②intelligence operation;③Based on the API standard, plugging gap plate height and width of plate (column) have been improved. At the same time the split style of gap column and sand-bed cylinder are designed;④the technology of special supercharge, sustained pressure and automatic regulatory pressure.⑤widening the limit of experimental temperature and experimental pressure. The test on temperature tolerance and pressure tolerance of the improved experimental apparatus shows that the instrument can be operated for dynamic experiments at 260℃, 38MPa. The pressurization SCM of YDL series were developed. Those series with temperature sensitivity and shear sensitivity are potential cross-linking, particle - fiber bridge blinding and time-lapse expansive materials. Once inside leakage channels, they can form crosslinking under the action of temperature and low shear flow (or static), and could release elastic energy to achieve efficient plugging. At the same time plugging material of high water loss which is better used at home was selected to evaluate. The advantages of the plugging agent are high fluid loss, fast filtration rate, good suspension stability, the solid particles of which the diameter is below millimeter and the quick and effective blocking of the leakage layer. HTHP dynamic plugging performance of YDL series products and high water loss plugging material selected were evaluated by new improved plugging experimental apparatus. The results showed that both of the two plugging materials have better seal fractured leakage effect, and especially are fit for plugging operation in the formation of deep wells with high temperature, which shows that the new improved plugging experimental apparatus is very effective in plugging evaluation.