The present invention relates to a method of determining present-day horizontal stresses in geological formations. The method comprises dividing the received well data in a plurality of contiguous sets of data i, a set of data For each set of data i in the plurality of sets of data, determining, at least parameters P.sup.i, a pressure in subsoil i, b.sup.i, a Biot coefficient i, ν.sup.i, a Poisson's ratio i, σ.sub.ν.sup.i, a vertical constraints in subsoil i, E.sup.i, a Young's modulus i, α.sup.i, a thermal expansion coefficient, and T.sup.i, and a subsoil temperature i. The method further comprises, i, computing and outputting the horizontal constraints.

Apparatus (10) and methods for combining time reversal and elastic nonlinearity of formation materials for qualtitatively probing for over-pressured regions down hole in advance of a well drilling bit, to determine the distance to the over-pressured region, and for accurately measuring pore pressure downhole in a formation, are described. Classical and reciprocal time reversal methods may be utilized to achieve these measurements.

A method for evaluating brittleness of a deep shale reservoir and a computer readable storage medium. The method includes determining a Rickman brittleness index of the deep shale reservoir and determining an effective pressure of the deep shale reservoir according to a pore pressure and an overlying formation pressure of the deep shale reservoir. The Rickman brittleness index is adjusted to obtain the brittleness index of the deep shale reservoir according to an exponential relationship of the brittleness index with the effective pressure of the deep shale reservoir. Inherent properties, such as rock brittle mineral content and the like, are better indicated by the Rickamn brittleness index, and then the brittleness index of the deep shale reservoir is obtained by utilizing the exponential relationship of the brittleness index with the effective pressure of the deep shale reservoir, to realize reasonable evaluation for the brittleness of the deep shale reservoir.

Disclosed herein are methods for predicting pore pressure in geological environments. Aspects of the disclosure describe details relating to performing geomechanical modeling for a target location in order to obtain a surrogate stress at the target location and predicting pore pressure by coupling velocity data (e.g., seismic and/or sonic) with the surrogate stress. Aspects of the disclosure can be used to obtain improved predictions of pore pressure in subsurface environments, especially in basins with complex geologic histories, and in practice to improve the safe design of casing, wellbore trajectory, and overall borehole stability.

Apparatus and methods for measurement of pore pressure in rock formations through an open, or cemented and/or cased, borehole are described. Such measurements are achieved using the Dynamic Acoustic Elasticity (DAE) method for characterizing nonlinear parameters by perturbing a selected rock formation volume with a High Amplitude, Low Frequency (HALF) acoustic strain wave, and probing this volume using a Low Amplitude, High Frequency (LAHF) acoustic wave. Time reversal techniques may be employed for focusing acoustic energy Into the formation in the vicinity of the pipe or open hole.

A method for determining a favorable time window of an infill well of an unconventional oil and gas reservoir, which comprises the following steps: S1, establishing a three-dimensional geological model with physical properties and geomechanical parameters; S2, establishing a natural fracture network model in combination with indoor core-logging-seismic monitoring; S3, calculating complex fractures in hydraulic fracturing of parent wells; S4, establishing an unconventional oil and gas reservoir model and calculating a current pore pressure field; S5, establishing a dynamic geomechanical model and calculating a dynamic geostress field; S6, calculating complex fractures in horizontal fractures of the infill well in different production times of the parent wells based on pre-stage complex fractures and the current geostress field; S7, analyzing a microseismic event barrier region and its dynamic changes in infill well fracturing; and S8, analyzing the productivity in different infill times, and determining an infill time window.

The present invention discloses a method for determining the characteristic parameters of stimulation intervals of multi-stage fractured horizontal well in unconventional oil and gas reservoir, comprising the following steps:

Step 1: Collect and sort out basic information and data of the well and reservoir;

Step 2: Collect and sort out daily test pressure data of the well;

Step 3: Collect and sort out daily test production data of the well;

Step 4: Split production data to obtain the production data of fracturing stimulation intervals at all stages;

Step 5: Select popular advanced production decline analysis software for oil and gas wells, input the basic information and data of the well and reservoir, the daily test pressure data and the production data of fracturing stimulation intervals at all stages obtained by splitting, and draw the double logarithmic curve of dimensionless production integral and dimensionless production integral derivative with time respectively;

Step 6: Fit and interpret the stimulation intervals at all stages to obtain the characteristic parameters of each stimulation interval. The method disclosed in the present invention can evaluate the reservoir characteristic parameters and fracture characteristic parameters of the stimulation intervals at all stages in an economical and efficient manner, and has important guiding significance for the efficient development of multi-stage fractured horizontal well after fracturing.

A method for estimating an anomalous pore pressure value at depth level of a first discontinuous interface between a first geological formation and a second geological formation to be drilled by means of a drilling apparatus comprising at least one bit, where said method is implemented by means of a system comprising at least one electro-acoustic transducer (20) mounted with said bit, at least one memory for containing observable data and at least one control processor for processing observable data contained in said at least one memory, where said at least one processor controls transmitting a signal transmitted at a given frequency, said at least one electro-acoustic transducer receives a received signal that said at least one processor records in said at least one memory, comparing it with pre-loaded observable data in said at least one memory and estimating the value of the anomalous pore pressure of the first discontinuous interface.

A method for determining a favorable time window of an infill well of an unconventional oil and gas reservoir, which comprises the following steps: S1, establishing a three-dimensional geological model with physical properties and geomechanical parameters; S2, establishing a natural fracture network model in combination with indoor core-logging-seismic monitoring; S3, calculating complex fractures in hydraulic fracturing of parent wells; S4, establishing an unconventional oil and gas reservoir model and calculating a current pore pressure field; S5, establishing a dynamic geomechanical model and calculating a dynamic geostress field; S6, calculating complex fractures in horizontal fractures of the infill well in different production times of the parent wells based on pre-stage complex fractures and the current geostress field; S7, analyzing a microseismic event barrier region and its dynamic changes in infill well fracturing; and S8, analyzing the productivity in different infill times, and determining an infill time window.

The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems, for determining a mudweight of drilling fluids in a hydrocarbon reservoir. One computer-implemented method includes: receiving pore pressure data of a rock formation in the hydrocarbon reservoir; determining permeability data of fractures of the hydrocarbon reservoir; determining Hoek-Brown failure criterion data; and determining a safe mudweight window based on the pore pressure data of the rock formation, the permeability data of the fractures, and the Hoek-Brown failure criterion data.