Stuck pipe is one of the main problems in drilling oil and gas reservoirs. It usually occurs in high pressure wells and leads to tremendous delays and costs in Iran, every year. Even if different techniques and guidelines have been developed to reduce the probability of occurrence of this phenomenon and these have saved drilling industry millions of dollars, they suffer from exclusive prediction of this event. The reason is that some of these techniques such as sag register incorporate one drilling parameter such as mud weight only.

In this paper, mud logging and daily reports of 75 wells in one of Iranian Southwest oil fields were studied. The performance of wells that did not experience stuck pipe was compared with the performance of those that led to stuck pipe.

Mud weight, yield point, plastic viscosity, initial gel strength, Marsh funnel viscosity, dial reading at 600 rpm, solid content, temperature, washout and the period that pumps do not need maintenance were employed to introduce a new parameter called Reducing Stuck Index (RSI). It was found that RSI is proportional to the mud weight, initial gel strength; yield point, solid content and temperature and also inverse of plastic viscosity, Marsh funnel viscosity and dial reading at 600 rpm to the power of 0.3. For this field, the comparison of RSI of the current well with those of drilled wells predicted the probability of occurrence of stuck pipe very well.

Monitoring RSI helps the driller to know whether the drilling process results in stuck pipe. If the situation is leading to stuck pipe, the drilling parameters can be managed in such a way that RSI lies in the safe range and stuck pipe is prevented.

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