Effects of temperature and pressure on the density of oil based drilling fluid:
1. Ask a kind of multi phase fluid, the drilling fluid is not only hot, but also compressible, so the density is a function of temperature and pressure. The test shows that, in general, with the increase of depth, p m gradually decreased. For the well temperature not high, Asakai, in the calculation of the bottom of the static fluid pressure, such as the neglect of temperature and pressure on the impact of drilling fluid density, will not produce a large error. For deep wells, however, the results show that the density of a water based drilling fluid at normal temperature and atmospheric pressure is 1.62g/cm3, but in the 6100m well (temperature 191, pressure 103.4Mpa) is reduced to 1.53g/cm3. At this point, the actual value of the static pressure of the bottom hole drilling fluid is more than the value of the Pm as a constant to decrease the 2.14MPa, so that the large error is enough to bring serious problems.
2. The thermal expansion and compressibility of oil base drilling fluid are significantly stronger than that of water base drilling fluid. At the same temperature, the density of the oil base drilling fluid is higher than that of the water base drilling fluid at the same temperature. Obviously, if the density of the two types of drilling fluid is the same in normal temperature and pressure, the density of the oil base drilling fluid is larger than that of the water base drilling fluid at high temperature and high pressure.
3. Because the oil based drilling fluid is used for deep well and all kinds of complex formation, and compared with water, oil can be much more compressible, so it is very important to study the general rule of the oil base drilling fluid density.
Method of reducing oil base drilling fluid density:
1. With the base oil dilution, to improve the oil / water ratio. This method makes the solid phase drilling fluid volume fraction decreases, viscosity and shear decreased.
2. With solid control equipment to remove some of the heavier materials.
3. Adding plastic microspheres. The filling plastic microsphere is made of phenolic resin or urea formaldehyde resin, the diameter of which is 50~300 m, and the density range is 0.1~0.25g/cm3. After entering into the drilling fluid, causing viscosity and shearing force increased, the filter loss reducing.