Causes and solutions of drilling sticking

Sticking, also known as differential pressure sticking, is the most common sticking accident in the drilling process, accounting for more than 60% of sticking failures.

Reasons for sticking:

(1)The drilling string has a long static time in the well;

(2) The pressure difference in the well is large;

(3) Poor performance of drilling fluid and poor quality of mud cake cause large friction coefficient;

(4) Poor borehole quality.

Characteristics of sticking drill:

(1) Sticking is in the static state of the drill string can occur, as for the static time will occur stuck, is closely related to the drilling fluid system, performance, drilling structure, hole quality, but there must be a static process.

(2)After sticking the drill, the position of the sticking point will not be the drill bit, but the drill collar or drill pipe.

(3)Before and after sticking, the drilling fluid circulation is normal, the import and export flow is balanced, and the pump pressure does not change.

(4)After adhering to the stuck drill, if the activity is not timely, the stuck point may move up, or even move straight near the casing shoe.

Prevention of sticking:

General requirements, drilling string stationary time should not exceed 3 minutes. The distance of each drill is not less than 2m, and the rotation is not less than 10 cycles. After the activity should be restored to the original suspension weight.

If the drill bit is at the bottom of the hole and cannot move and rotate, it is necessary to press 1/2-2/3 of the suspended weight of the drill tool on the drill bit in order to bend the lower drill string, reduce the contact area between the drill string and the wall mud cake, and reduce the total adhesion.

During normal drilling, such as the failure of the faucet or hose, the kelly pipe must not be seated at the wellhead for maintenance. If stuck drilling occurs, it will lose the possibility of pressing down and rotating the drill string.

Treatment of sticking drill:

(1) Strong activity

The sticking becomes more and more serious with the extension of time. Therefore, in the initial phase of the discovery of stick, the maximum force should be carried out within the safe load of the equipment (especially the derrick and suspension system) and the drill string. It does not exceed the safe load limit of the weak link, and the weight of the whole drill string can be pressed on the lower pressure, and appropriate rotation can also be carried out, but it cannot exceed the limit number of torsion turns of the drill pipe.

(2)Unlock the card

If the drill string has a jar while drilling, it should immediately start the upper hammer up or start the lower hammer down to solve the card, which is more concentrated than the simple up and down force.

(3) Soak the release agent

Immersion release agent is the most commonly used and important way to release stuck drill. There are many kinds of jam release agents, broadly speaking, including crude oil, diesel oil, oil compounds, hydrochloric acid, soil acid, water, salt water, alkali water, etc. In a narrow sense, it refers to a special solution composed of special materials for lifting the adhesion stuck drill, there are oil-based, there are water-based, their density can be adjusted as needed. How to choose the release agent, depending on the specific situation of each region, low pressure well can be selected at will, high pressure well can only choose high-density release agent.