| Abstract |
Directional wells in geothermal exploitation are preferred to vertical wells since unlike vertical wells more than one well can be drilled on a site, they can be drilled around obstacles and the wells have higher probability of intersecting more production zones. To effectively drill the directional wells, the wells are drilled towards a target as per required inclination and azimuth. To control the direction of the well and the rate of drilling to ensure the wells are drilled safely and to completion, a proper design of the bottom hole assembly (BHA) and drilling parameters should be done. The designs to achieve the directional target vary from one well to another depending on the formation being drilled. At Menengai, directional wells are kicked-off with a mud motor in the 12¼″ hole section at a depth of 400m to about 500m. Hold the angle to a depth of 800m and then drop the angle slightly to 9⅝″ casing depth. For the entire 8½″ hole section, to the angle is dropped slightly to the total depth of the well. This paper looks at designs for the bottom hole assemblies and the drilling parameters that were used for a sample of directional wells drilled to completion. Any unforeseen challenges like getting stuck, drill string failure, high drilling torque while drilling and the probable causes of such drilling challenges. The actual directional well trajectories in comparison to the planned directional trajectories will also be considered to determine the effectiveness of the different BHA designs in deviation control. From the analysis of the designs, a proper BHA design will be proposed for each of the hole sections while kicking off, holding angle, dropping the angle and building the angle. The paper uses data from 2 directional wells, MW21A and MW09B. The BHA’s used while drilling the 2 wells will be analyzed for their effectiveness in the Menengai formation. |