Abstract: A method of calculating the likely positions of structures in a region of the earth's crust includes defining the region in the earth's crust; creating a first structural model of the region from seismic data with uncertainties and correlations; creating a second structural model of the region from measurements in a wellbore with uncertainties and correlations; creating a third structural model of the region from measurements in a volume around the wellbore measured from the wellbore with uncertainties and correlations; defining constraining equations for the first, second and third structural models; and using said constraining equations, calculating likely positions of structures in the region, and likely uncertainties and correlations relating to the positions.

Abstract: A method of performing quality control on a subsurface model of a subterranean region includes providing a plurality of types of data relating to subsurface characteristics in the subsurface model outside of one or more wellbores in the region, the plurality of types of data including wellbore data obtained from one or more measurement instruments located within at least one of the one or more wellbores, performing an analysis on the data to determine if there is an error or errors in the data; if an error is detected, searching for the cause of the error; if the cause of the error is detected, correcting the error; if the cause of the error is not detected, either ignoring the data containing the error or including in the model the data containing the error and allocating to the data containing the error an increased prior uncertainty thus reducing the influence on the model of the data containing the error.

Abstract: There is provided a method of assessing the quality of subsurface position data and wellbore position data, comprising: providing a subsurface position model of a region of the earth including the subsurface position data, wherein each point in the subsurface position model has a quantified positional uncertainty represented through a probability distribution; providing a wellbore position model including the wellbore position data obtained from well-picks from wells in the region, each well-pick corresponding with a geological feature determined by a measurement taken in a well, wherein each point in the wellbore position model has a quantified positional uncertainty represented through a probability distribution; identifying common points, each of which comprises a point in the subsurface position model which corresponds to a well-pick of the wellbore position data; deriving for each common point a local test value representing positional uncertainty: selecting some but not all of the common points and deri