Supporting the teaching of Earth sciences at all levels
Experiment: Mike Tuke              Realised by: Julian & Phillipa Priddle                  Sponsor: PESGB


This virtual activity involves drilling boreholes to try to describe an oil trap and to suggest the best place to locate a production well, based on this data. Before starting the activity it is a good idea to see what oil traps look like. Here are two websites that will explain the geological formations that allow oil to be trapped underground. Look at these before going further with this activity. aps
When you run the activity you will be asked to choose one of four locations. Each of these has a grid with numbers across the top and letters down the side. This represents an area 2km by 2km and it is flat so you get no clues to tell you what structure is underneath. Each location is provided with a pdf location file for your data. The oil and gas are trapped in the sandstone layer. The green cells are for measurements of the top of the sandstone layer and the white cells for the base. You are only allowed 30 holes because drilling is expensive. It is a good idea to spread your first ten bore-holes out and then look to see if you can see any changes in depth which will help you to decide where to put the rest of the holes.  It is not easy to work out what is happening underground from just a few pieces of data. 1 Select your area by pressing one of the buttons on the right hand side. This will select the correct location pdf. Print this out.. 2 Press animation 3 Select the same location in the animation 4 Press "return to grid" 4 Select a borehole site on the grid 5 Watch the borehole being drilled and record the depth to the top and bottom of the sandstone 6 Repeat instructions 4 and 5 until you have completed 30 boreholes. 7 Look at your record sheet and see if you can work out the structure of the sandstone and which of the 3D diagrams (below) that it matches. One way to help with this is to try to draw contours (lines of equal depth) for the top sandstone surface. Remember that there may be faults where the depths suddenly alter.
location 1 location 2 location 3 location 4
When you have worked out which type of oil trap you have, you need to decide where you would drill your well. Remember that there is likely to be gas in the top of the trap (see the diagram of the oil trap below) and that as the oil is pumped out the gas will expand and push the oil down. A well drilled at the top of the trap will have to be moved which costs more money. It is usual to locate the well to one side, so that oil can be pumped continually.
Diagram of an oil and gas trap