1. Properly shut
Once overflow occurs, follow the correct procedure should first shut. To ensure that critical moment can quickly and correctly shut, shut the need to develop a reasonable program, and regularly conduct well control drills. Once overflow occurs, it should be shut as soon as possible. When discovered by the overflow can quickly benefit program control wellhead shut-in are:
(1) control the wellhead, the well control work in a proactive, conducive to safe killing to prevent blowouts, help protect ground personnel and equipment and the surrounding environment.
(2) Suppression of formation fluids into the well to continue.
(3) may have more to maintain the well workover fluid, reducing the shut-in pressure, and can strike shut-in pressure data.
(4) can be more accurately determine the formation pressure.
(5) can accurately determine the kill fluid density, ready to kill for the organization.
2. Key to shut wells
1) shut to timely and decisive
Event kicks, the more quickly shut, kicks smaller; the smaller the kick, the easier to control, general control program is also more secure.
To quickly and decisively shut, it must frequently BOP drills so that all positions clear their responsibilities, master shut-in procedures under various conditions. According to "China National Petroleum Corporation Oil & Gas Downhole well control regulations" requirement, underground work force should be based on the content of the job, such as when to rotate the job, from under the pipeline, when the rod (drill pipe, rod), since under drill collars, tool, only a small amount of time the well pipe string cable (wire) overflow of six conditions, sub-post perforation occurs when and empty well, according to BOP regular exercise program. Team work should be carried out under different conditions BOP drills and make commenting and recording BOP drills. Exercise records include: team, date and time, working conditions, speed drills, participants, and other problems, and commenting. Only members can reach a tacit understanding with the team, in practice there is a kick or blowout occurs, in order to achieve fast and accurate shut.
2) must not exceed the maximum limit set in the shut-in pressure
Shut-in casing pressure maximum allowable limit is the maximum pressure without damaging BOP equipment, casing or formation conditions, the well can bear.
BOP pressure rating of selection, construction horizon should not be less than the highest intensity of formation pressure and pressure resistant casing used, and casing spool rated working pressure of the smallest in principle.
Compressive strength of the casing is also known as the internal pressure of the yield stress, most of the value is easy to be found. It depends on the casing diameter, wall thickness and casing materials. In the "China National Petroleum Corporation Oil & Gas Downhole Well Control provisions" expressly required to allow shut casing pressure must not exceed a maximum of 80% within the casing pressure strength. Formation can withstand pressure depends on the well off and its burst pressure column pressure, depth and the depth under. Casing shoe is usually the weakest part of the openhole section.
3. Shut-in method
Currently shut methods used are mainly two: soft and hard shut-off wells.
Soft shut is when an overflow occurs or blowout, at the throttle channel is turned on, the case of the other flanking channel closed closed BOP and close the throttle. The advantage of this approach is shut to avoid water hammer effect due to a sudden shut-generated, if the casing pressure becomes too high, you can also take other well control method (such as low-pressure throttle pressure, etc.), so shut safer. The disadvantage is longer shut, shut-in will continue the process of formation fluids to enter the well.
Hard shut is when an overflow occurs or blowout at Choke valve, Stone and other flanking channel fully closed case closed BOP. The advantage of this approach is shut shut relatively short time, you can quickly stop the formation fluid into the well. The disadvantage is prone to shut the water hammer effect, so that the wellhead, casing and formation of the sharp increase in pressure, even more than the rated working pressure wellhead, the compressive strength of the casing and the formation of anti-fracture pressure, resulting in loss of control wellhead . As for the specific use of which method is shut, one is to be in accordance with the requirements of Party; on the other hand depends on the size and configuration of the well blowout preventer (or kick) scale to decide.
4. Division of responsibility
Discover kick or blowout, decided to shut consider many factors, such as depth, kicks size, position the casing shoe, BOP ability surroundings, workover rigs and drilling crews and security personnel. Supervision, the captain, and each class squad technicians should take place before the kick, to discuss the various conditions of the shut-good program. Staff to the division in charge of the team, in close cooperation, can in the shortest possible time, safely and quickly shut the wells.