Figuring out Cutting Lag Time and Receiving of Core Cuttings from Core Barrel During Drilling of Formations

الملخص

Most of us use oil, and it is difficult to imagine the modern world without oil, but oil and gas are not, easy to find and get out of the earth. It is of course we cannot see the oil which is trapped deep, down in the ground. Geologists must study rocks carefully, and when they know rocks in a certain place, containing oil or gas, drilling processes will then take place. Oil and gas are obviously not rocks, but they are, derived from rocks, like sedimentary rocks.
Petroleum occurs in the pores of sedimentary rocks, the most common are, sandstones, limestone and dolomites, which may contain porosity and permeability filled with oil, gas and water and they can act as reservoir rocks. Most drilling oil companies require a mudlogging unit on their wells, to provide identification and evaluation, of oil and gas bearing formations, during drilling operations. The main, source of geologic data are the cuttings of rocks produced in the process of drilling a well, whears core cuttings are a cylindrical rock sample of different diameters, used to understand, the subsurface conditions, like rock type, pore fluids and detailed reservoir characteristics. In rotary drilling, the drilling fluid is pumped, from the surface, down inside the drill string, and through vents in the, drilling bit at the bottom hole, this fluid returns, back to the surface through the annulus between, the drill string and the walls of the hole carrying well cuttings from the bottom hole up to the surface, were they are collected. There is always a time Lag between when the formation is drilled and when cuttings returns back to the surface, this time is called "lag time". This time used is to ascertain the true representative depth from which cuttings come, controlled by the slip velocity of drilling fluid. The objective of this study is to calculate and figure out the lag time
required for well cuttings to reach from the bottom of the well up to the surface and receiving core cutting from core barrel during drilling formation which produce cuttings. A case study for the well (f- 22) drilled to a total depth of 12000 feet, and a core cuttings are taken in this well through the Gargaf formation represents a reservoir rock in this well, and figuring out the lag time of well cuttings form the bottom of the well up to surface