“Weight on the bit” is the amount of force exerted on a drill bit in an oil well. The weight is measured by lowering the entire drill string and collars onto the bit, and the decrease in weight is designated as “tip weight”. This is different from conventional drilling where direct pressure is exerted on the drill bit. The weight-on-bit value is typically measured using a drill string weight gauge or MWD sensors.
“Weight on the bit” is a quantitative term used to express the amount of weight or force exerted on the drill bit at the bottom of an oil well by lowering the drill string and collars onto the bit. To cut the rock, the drill bits used in these operations are forced against the bottom of the well by the weight of the entire drill string and, in particular, specially designed heavy sections of pipe known as drill collars. When the entire assembly is still suspended from the tower, the weight is weighed and the weight noted. The rope is then carefully lowered until the tip is at the bottom of the well. From that point on, the weight of the hanging rope is closely monitored as it progressively decreases, the decrease in the initial reading as the drill bit takes the weight of the collars and rope is designated as the “tip weight”.
To understand the concept of weight at the bit, it is necessary to understand the difference in the force applied between conventional drilling and oil well drilling. For example, to drill a piece of wood with a normal domestic electric drill, the handyman exerts direct pressure on the drill, and consequently on the tip of the bit, pushing against it. In the case of deep drilling of wells and wells, this type of action is impractical. In these cases, the drill bit is lowered to the bottom of the well where it is forced against the underside of the hole by constantly lowering weights on it as it rotates. The amount of weight added to the drill bit section is known as the “tip weight”.
To accomplish this rather complex operation, the entire drill string, consisting of the drill bit section, drill pipe and drill collars, is suspended with the bit raised from the bottom of the well. The exact weight of the combined set is carefully noted and the string is lowered until the bit is just at the bottom of the hole. Of course, as the string drops, the drill bit begins to absorb some of the weight of the drill string, with a corresponding decrease in suspended weight. For example, if the initial suspended weight was 200.000 lbs (90.718 kg) and the reading once some of the weight is on the tip is 150.000 lbs (68.038 kg), then the weight-on-bit value is 50.000 lbs (22.679 kg).
These readings are typically taken from a drill string weight gauge located on the drill rig. Some indicators are simple single scale instruments which require the operator to continuously calculate the weight on the bit values as in the example of the previous paragraph. Others are a little more functional and have dual scales: a primary scale that indicates hanging weight and a secondary scale for tip weight. The secondary scale is zeroed once the bit hits bottom and essentially reads backwards as the suspended weight decreases, with the operators simply reading the weight-on-bit values directly from it. Alternatively, Measurement While Drilling (MWD) sensors positioned downhole just above the drill section can also be used to send more accurate drill weight values to a surface readout interface.
Protect your devices with Threat Protection by NordVPN
