Calculation of Harmful Low Density Solids Content in Oil Base Drilling Fluids Using Linear Regression Method

With the large scale development of shale gas, high density oil base drilling fluids are finding wide application in shale gas drilling. During drilling, small particles are continuously entering into the drilling fluid, greatly affecting the performance of the drilling fluid. Presently there is no method for calculating the drilled cutting content of oil base drilling fluids. The standard GB/T 16783.2 only gives a method of calculating the content of low density solids, which is unable to differentiate the wanted low density solids and the unwanted harmful low density solids. By comparing the solids contents of drilling fluid taken from a well and the mud freshly made in laboratory, a method for calculating the content of harmful low density solids was developed through linear regression. This method was also checked for its accuracy using muds taken from fields. Errors between the solids content obtained from linear regression and the solids content actually measured were less than 3%, indicating that this method can be used to accurately calculate the content of harmful solids. This simple method has provided an important standard on which the properties of oil base drilling fluids can be maintained. Small calculation errors make the method valuable and feasible to field application.