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In well control, differential pressure is defined as the difference between the formation pressure and the bottom hole hydrostatic pressure. [12] These are classified as overbalanced, underbalanced or balanced. Overbalanced – The hydrostatic pressure exerted on the bottom of the hole is greater than the formation pressure. i.e. HP > FP
Formation fluid can enter the wellbore if the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the formation being drilled (pore pressure). [1] [2] Oil well control also includes monitoring a well for signs of impending influx of formation fluid into the wellbore during ...
A diagram of a pumpjack. A pumpjack is the overground drive for a reciprocating piston pump in an oil well. [1] It is used to mechanically lift liquid out of the well if there is not enough bottom hole pressure for the liquid to flow all the way to the surface. The arrangement is often used for onshore wells. Pumpjacks are common in oil-rich areas.
Logging while drilling (LWD) is a technique of conveying well logging tools into the well borehole downhole as part of the bottom hole assembly (BHA).. Although the terms Measurement while drilling (MWD) and LWD are related, within the context of this section, the term MWD refers to directional-drilling measurements, e.g., for decision support for the smooth operation of the drilling, while ...
It works on the principle that the hydrostatic head of the "kill fluid" or "kill mud" will be enough to suppress the pressure of the formation fluids. Well kills may be planned in the case of advanced interventions such as workovers, or be contingency operations. The situation calling for a well kill will dictate the method taken.
Injected gas aerates the fluid to reduce its density; the formation pressure is then able to lift the oil column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas-lift equipment. [1]
The full name for this most common type of downhole safety valve is a Tubing Retrievable Surface Controlled Sub-Surface Valve, shortened in completion diagrams to TRSCSSV. If a tubing retrievable valve fails, rather than go to the expense of a workover, a "wireline retrievable" valve may be used instead.
A diagram showing forces at work during differential sticking. The small black arrows represent pressure exerted on the drill pipe from the wellbore, the red arrows represent pressure exerted on the pipe from the formation (smaller than in the wellbore) and the large black arrow represents the net force on the pipe, which is pushing it into the wall.