Shaanxi Wande Oil introduces the role of mud

Shaanxi Wande Oil introduction mud is drilling wash fluid. Well washing is a key link in drilling. Well washing 

and rock breaking are carried out simultaneously. Shaanxi Wande Oil explained that drilling can not continue

 if the mud circulation stops, and the mud circulation purification system is a major part of the drilling equipment.

First, wash the well

In drilling, timely carrying cuttings out is one of the important conditions for safe and fast drilling, mud carrying 

cuttings to go through two processes, the first process is to make the cuttings leave the bottom of the well and

 enter the ring space; The second process relies on the  upwelling of mud to bring cuttings out of the wellbore to

 the platform.

1, clean the bottom of the well debris

At present, the jet technology is used to clean the rock debris at the bottom of the well. The so-called injection

 technology is to use a multi-bit nozzle to spray out a powerful mud jet, with a high injection speed to impact 

the bottom of the hole debris, so that the rock debris left the bottom   of the hole to keep the bottom of the

 hole clean.

2. Carry cuttings

The density of cuttings is generally 2.3~2.7 g/cm3, and the density of mud is 1.05~2 g/cm3, and the cuttings

 are subject to buoyancy less than their weight in the mud, so the cuttings will sink in the mud. In order to make 

the cuttings back up, the mud back up speed must be greater than the cuttings sinking speed, and the higher 

the mud back speed, the more favorable to carry cuttings. However, excessive mud return speed will cause pressure

 loss and erosion of the well wall, so it is necessary to determine a reasonable  annular return speed, not only 

toeffectively  carry cuttings, but also to drill fast, high-quality and safe.

The rheology of mud has an important effect on well washing. According to the need of rock carrying, mud 

must have good shear dilution characteristics.

Second, suspended rock debris

When the mud circulation is suddenly interrupted for some reason, the cuttings in the annulus will sink, and 

the drill string will be buried in serious cases (that is, stuck), or in order to prevent the cuttings from sinking, 

the mud is required to have good thixotropy, that is, when the mud is stationary, it has a large cutting force 

and can suspend the cuttings in the hole.

3. Stabilize the well wall

Borehole stability and borehole regulation are the important basic conditions for high quality and fast drilling, 

and also the basic  foothold of mud measures. 

The composition of the mudmust have a strong inhibition effect on the hydration expansion and dispersion 

of the  mud shale encountered. 

The filtration performance of the mud should be conducive to the formation of thin and tough mud cake

 on the wall  of the hole, and ensure that the flow rate of the annular mud does not reach the turbulent state, 

so as to avoid the   turbulent mud to have a greatererosion effect on the wall of the hole.

4. Other functions

The mud density can be adjusted in a wide range to establish a liquid column pressure that is balanced with

 formation pressure  and prevent blowout, loss, well collapse, stuck and other downhole accidents. Balanced

 pressure drilling is not only a measure to prevent the occurrence of external conditions, but also  plays an

 important role in bottom hole purification, increasing drilling rate and reducing the damage of mud to the 

reservoir.