The shale density meter is an instrument to measure the density of shale.
By measuring the density of mudstone, you can know the pressure change of drilled strataand predict the possible formations with abnormal pressure. The abnormal pore pressure of formations is extremely dangerous to oil wells and it may cause accidents such as well kick, well blowout, well lost, shrinkage of borehole diameter, bit freezing and so on. Characteristics of mudstone to produce ultra high pressure are that the density of mudstone decreases, deviating from normal density trend line of mudstone. In general, the resistivity and acoustic velocity of formations with abnormal pressure are also different and as a result, the resistivity log and acoustic log can be used to detect them. But these log curves can be obtained only after the drilling is complete. Therefore, a method to immediately predict ultra high pressure formations is required, namely, the method to measure the density of mudstone is used to predict abnormal pore pressure of formations.

Operating principle

Measuring mudstone density is to monitor abnormal pressure formation. According to the regulation of mudstone compaction, the porosity of mudstone decrease in exponential function way when the depth are increasing in normal condition, mudstone density increases with the increase of depth. When meeting pressure transition zone and high pressure layer that would cause under compaction, the porosity would higher and density would lower than normal condition. Because the density of mudstone has that change regulation, it can be measured by mudstone debris which digs from underground by designed well height. Setting normal pressure formation's mudstone density curve as base line, other lines which are excursion form this base line will be seemed as pressure abnormal. The higher excursions that curve have, the higher abnormal pressure the layer gets. The start point of excursion is the peak point of transition zone.