This application relates to methods and apparatus for monitoring a geological formation that is or has been subjected to steam injection using a distributed fibre optic sensor apparatus to perform distributed fibre optic sensing on an optical fibre deployed in a borehole running through the geological formation to acquire a first set of measurement signals being indicative of disturbances acting on each of a plurality of longitudinal sensing portions of the first optical fibre where at least part of the optical fibre is disposed adjacent to at least a first electrode spaced apart from a second electrode and the first and second electrode are separated by a void that is filled with a gas and an electrical source applies a potential difference to the first and second electrodes such that an ionisation event within the gas results in an avalanche multiplication.

A technique facilitates use of acoustic measurements to enable geo-steering during a well operation. A steerable well string is provided with acoustic systems used to collect data which is then processed to determine geo-steering inputs. In some applications, the well string may comprise a coiled tubing drilling tool. The coiled tubing drilling tool or other well string tool is combined with an azimuthally distributed pitch-catch micro-sonic sensor system and an azimuthally distributed ultrasonic pulse-echo transducer system. Data from these two systems is provided to a processing system which processes the data to determine, for example, real-time, geo-steering inputs. These inputs may then be used to more effectively steer the coiled tubing drilling tool or other well string tool.

A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level. In various embodiments, the residual measurement errors are reduced from a first value that does not match the selected quality level to a second value that are consistent with the selected quality level.

A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level. In various embodiments, the residual measurement errors are reduced from a first value that does not match the selected quality level to a second value that are consistent with the selected quality level.

A distance of a water flow path and a velocity of the water flow is calculated using pulsed neutron data and noise data. The two distance and velocity values are compared with each other to obtain a first calculated distance and a first calculated velocity. The distance of the water flow path and the velocity of the water flow are calculated using Doppler data. The distance and velocity values are compared with the first calculated distance and first calculated velocity to obtain a second calculated distance and velocity values. The distance of the water flow path and the velocity of the water flow are calculated using temperature data. The distance and velocity values are compared with the second calculated distance and velocity to determine a distance of a cement interface and a velocity of a water flow in the cement interface.

A distance of a water flow path and a velocity of the water flow is calculated using pulsed neutron data and noise data. The two distance and velocity values are compared with each other to obtain a first calculated distance and a first calculated velocity. The distance of the water flow path and the velocity of the water flow are calculated using Doppler data. The distance and velocity values are compared with the first calculated distance and first calculated velocity to obtain a second calculated distance and velocity values. The distance of the water flow path and the velocity of the water flow are calculated using temperature data. The distance and velocity values are compared with the second calculated distance and velocity to determine a distance of a cement interface and a velocity of a water flow in the cement interface.

The present disclosure provides a method for recovering a porosity evolution process of sequence stratigraphy of carbonate rocks. The method comprises: a step of establishing a sequence stratigraphic framework of carbonate rocks; a step of dividing diagenetic stages; a step of simulating diagenesis and porosity evolution with increasing reservoir thickness and continuous superposition of multiple reservoirs during cyclic rise and fall of sea level to obtain a simulation result; and a step of calculating the porosity evolution in space over time by using the simulation result as initial values for simulation of diagenetic evolution process and simulating in stages and continuity the multi-stage diagenetic evolution process that the carbonate rock strata undergo after sediment based on the divided diagenetic stages. Compared with the traditional recovery of single reservoir porosity with time evolution, the method fully considers the superposition effect of multiple upper reservoirs in the process of reservoir sedimentary-diagenesis.

A system that is usable with a well includes a telemetry network; a plurality of receivers that are arranged in groups; and a plurality of concentrators that are associated with the groups of receivers. A given concentrator is adapted to acquire data from an associated group of the receivers, and the concentrators communicate the data to an Earth surface of the well using a plurality of frequencies that are allocated among the concentrators.

Inversion techniques are provided for imaging subsurface regions from geophysical data sets. The inversion techniques provide a geophysical data set containing data measured from a subsurface region to an objective function. These techniques further optimize the objective function to invert for an implicitly represented geologic structure of the subsurface region and at least one geophysical parameter of the subsurface region. In addition, the inversion techniques use a computer system to present results produced by the objective function optimization.

Inversion techniques are provided for imaging subsurface regions from geophysical data sets. The inversion techniques provide a geophysical data set containing data measured from a subsurface region to an objective function. These techniques further optimize the objective function to invert for an implicitly represented geologic structure of the subsurface region and at least one geophysical parameter of the subsurface region. In addition, the inversion techniques use a computer system to present results produced by the objective function optimization.