|Title||The value of spatial information for determining well placement: A geothermal example|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Trainor-Guitton W.J, Hoversten G.M, Ramirez A., Roberts J., Juliusson E., Key K, Mellors R.|
|Type of Article||Article|
|Keywords||electrical-resistivity; field; methodology; reservoirs; seismic amplitude|
We have developed a spatial, value of information (VOI) methodology that is designed specifically to include the inaccuracies of multidimensional geophysical inversions. VOI assesses the worth of information in terms of how it can improve the decision maker's likelihood of a higher valued outcome. VOI can be applied to spatial data using an exploration example for hidden geothermal resources. This methodology is applicable for spatial decisions for other exploration decisions (e.g., oil, mining, etc.). This example evaluates how well the magnetotelluric (MT) technique is able to delineate the lateral position of electrically conductive materials that are indicative of a hidden geothermal resource. The conductive structure (referred to as the clay cap) represented where the geothermal alteration occurred. The prior uncertainty of the position of the clay cap (drilling target) is represented with multiple earth models. These prior models are used to numerically simulate the data collection, noise, inversion, and interpretation of the MT technique. MT's ability to delineate the correct lateral location can be quantified by comparing the true location in each prior model to the location that is interpreted from each respective inverted model. Additional complexity in the earth models is included by adding more electrical conductors (not associated with the clay cap) and deeper targets. Both degrade the ability of the MT technique (the signal and inversion) to locate the clay cap thereby decreasing the VOI. The results indicate the ability of the prior uncertainty to increase and decrease the final VOI assessment. The results also demonstrate how VOI depends on whether or not a resource still exists below the clay cap because the clay cap is only a potential indicator of economic temperatures.