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Jumat, 29 Maret 2019

Petroleum Exploration Drilling – An Overview


Petroleum Exploration Drilling – An Overview

Geologists & Geophysicists have agreed on the existence of a “prospect”, a potential field. In order to find out if Hydrocarbons are indeed trapped in the reservoir rock, we have to drill the prospect location.

Setting up – Installation
The best position for set up drilling equipment is determined. The drilling conducted, sometime difficult, small diameter (20-50cm) the hole generally down to depth 500-4000meters. Exceptionally, certain wells exceed 6000m.

The Drilling Well
The derrick is the visible part of the drilling rig. It is used to vertically introduce the drill strings down the hole. These drill string are made up of metallic tubes screwed end to end. They transmit rotating movement (rotary drilling) to the drilling tool (the drill bit) and help circulate a liquid (mud) down to the bottom of the well.

The Drillbit some are tric-cone, through the drill pipes, at the extremity of which the drill bit rotates, a mud is injected, which the mud engineer prepares and controls. This mud cools the drill bit and consolidates the sides of the borehole. Moreover it avoids a gushing of oil, gas or water from the layer being drilled, by equilibrating the pressure. Finally, the mud cleans the bottom of the well, carries the rock fragments (cuttings) to surface.

The Geologist examines these cuttings to discover the characteristics of the rocks being drilled and to detect eventual shows of HC. Sometime core sample is taken. The core gives the inclination of layers, structure, permeability, porosity, fluid, and fossil. The measurments down the hole called logging, commonly lowering electronic tools into the well to measure the physical parameters of formation rocks.

The well completion and Test
When HC are found (discovery), and the pressure is sufficient to allow them come to the surface naturally and calibrated by test. The quantity recoverd is measured, as are changes in pressure at the bottom of the well. In this way, a little more knowledge is gained about the probable productivity of the field.

The assessment
If the field is promising, the exploration team ends the first discovery well and goes on to drill a second, even several others, several hundred or thousand meters near the well. The exploration team is able to refine its knowledge about the characteristic of the field.

The Different types of Platform offshore
The decision to stop drilling is made only when all these appraisal wells have provided sufficient information or to envisage future production.


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