Abstract: A method includes identifying a wellbore that extends from a terranean surface and to a subterranean formation that includes a saline aquifer; injecting, through the wellbore, a predetermined volume of freshwater into a portion of the saline aquifer adjacent the wellbore to create a freshwater ring about the wellbore in the subterranean formation; and subsequent to injecting the predetermined volume of freshwater, injecting a carbon dioxide fluid, through the wellbore, and into the subterranean formation for sequestration.

Abstract: A method of analyzing a caprock of an aquifer includes determining, using a laboratory measurement device, a threshold hydraulic gradient of the caprock at which brine flows vertically in the caprock. The method further includes determining a breakthrough pressure of the caprock, wherein the breakthrough pressure reflects a difference between a CO2 pressure in the aquifer and a brine pressure in the caprock. The method further includes calculating, via a computing system that includes one or more hardware processors, an effective breakthrough pressure of the caprock based on the threshold hydraulic gradient and the breakthrough pressure, wherein the effective breakthrough pressure accounts for non-Darcy flow of the brine within the caprock.

Abstract: Apparatus and methods for determining caprock integrity. The testing apparatus for performing the method including a core container in fluid communication with an upstream reservoir and an upstream pump, and further in fluid communication with a downstream reservoir and a downstream pump. The method including determining threshold hydraulic gradient of a caprock core sample using the testing apparatus.

Abstract: Methods and systems are disclosed. The methods may include obtaining, from a subterranean region of interest, a rock sample having a rock type and defining a sequence of pore pressure, confining stress (PPCS) pairs such that a sequence of effective stresses monotonically changes. The methods may further include determining a sequence of permeabilities by subjecting the rock sample to the sequence of PPCS pairs and determining a relationship between the sequence of PPCS pairs and the sequence of permeabilities. The methods may further still include determining a parameter using the relationship and a permeability model, where the permeability model includes the parameter and determining an in situ permeability for an in situ rock in the subterranean region of interest using, at least in part, the parameter and the permeability model, where the in situ rock is of the rock type.

Abstract: A method may include obtaining reservoir data, hydraulic fracturing data, and static wellbore data for a geological region of interest. The method may further include obtaining temporal production data for the geological region of interest. The temporal production data may include a predetermined production rate with respect to a predetermined period of time. The method may further include determining various temporal features based on the temporal production data and an extraction process. The extraction process may include a deconvolution function that separates a portion of the temporal features from the predetermined production rate. The method may further include determining, using a machine-learning model, predicted hydrocarbon-in-place (HIP) data for the geological region of interest using the reservoir data, the hydraulic fracturing data, the static wellbore data, and the temporal features. The method may further include transmitting a command to a well control system based on the predicted HIP data.

Abstract: Wellbore treatment fluids are provided that include an aqueous component and an amphiphilic hyperbranched copolymer comprising the polymerized reaction product of at least a first monomer and a second monomer, where the first monomer comprises at least one surface reactive end group chosen from the group consisting of carboxylates, phosphonates, sulfonates, and zwitterions. Also provided are methods of modifying subsurface energy of a carbonate formation using the wellbore treatment fluids.

Abstract: A method and a system for predicting well production of a reservoir using machine learning models and algorithms is disclosed. The method includes obtaining a training data set for training a machine learning (ML) model and selecting an artificial neural network model structure, the model structure including a number of layers and a number of nodes of each layer. Further, the method includes generating a plurality of individually trained ML models and calculating a model performance of each trained model by evaluating a difference between a model prediction and a well performance data. The plurality of top-ranked individually trained ML models is constrained using one or multiple known physical rules. A plurality of individual predicted well production data is generated using the geological, the completion, and the petrophysical data of interest and a final predicted well production data is generating based on the plurality of individual predicted well production data.

Abstract: Methods and systems are disclosed. The methods may include determining a first sequence of permeabilities by subjecting a rock sample to a first sequence of confining stress, axial stress, pore pressure (CSASPP) triplets and determining a first rock parameter using the first sequence of permeabilities, the first sequence of CSASPP triplets, and a first permeability model. The methods may further include determining a second sequence of permeabilities by subjecting the rock sample to a second sequence of CSASPP triplets and determining a second rock parameter using the second sequence of permeabilities, the second sequence of CSASPP triplets, and the first permeability model. The method may still further include determining an in situ permeability for an in situ rock based on an initial permeability, a second stress sensitivity parameter, a first stress sensitivity parameter, a confining stress value, axial stress values, a pore pressure value, and a second permeability model.

Abstract: Systems and methods for analyzing and modeling natural gas flow in subterranean shale reservoirs. In some embodiments, methodologies and techniques for determining and modeling natural gas flow in shale formations using methodologies and techniques capable of determining natural gas properties related to dual-continuum flow, permeability, and pressure within a subterranean shale reservoir. In some embodiments, the natural gas properties are determined by subjecting a subterranean shale reservoir sample to pulse-decay analysis. In certain embodiments, the methodologies and techniques described may be used in various reservoirs exhibiting macroporosity and microporosity, such as fractured reservoirs and carbonate reservoirs composed of reservoir fluids.

Abstract: A method for determining a matrix permeability of a subsurface formation, including the steps: acquiring a core from the subsurface formation, imposing a fluid to the core until the core is saturated with the fluid, conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and determining the matrix permeability from decays of the pressure-pulses on the upstream side and downstream side, respectively.

Abstract: Systems and methods for analyzing and modeling natural gas flow in subterranean shale reservoirs. In some embodiments, methodologies and techniques for determining and modeling natural gas flow in shale formations using methodologies and techniques capable of determining natural gas properties related to dual-continuum flow, permeability, and pressure within a subterranean shale reservoir. In some embodiments, the natural gas properties are determined by subjecting a subterranean shale reservoir sample to pulse-decay analysis. In certain embodiments, the methodologies and techniques described may be used in various reservoirs exhibiting macroporosity and microporosity, such as fractured reservoirs and carbonate reservoirs composed of reservoir fluids.

Abstract: A system and methods for predicting well performance are disclosed. The method includes obtaining first geoscience data and first performance data, obtaining second geoscience data and second performance data, and obtaining new geoscience data for a new well. The method further includes training a first neural network and determining predicted second performance data using the first neural network. The method still further includes determining a residual between the second performance data and the predicted second performance data and training a second neural network. The method still further includes determining predicted new performance data for the new well by inputting a subset of the new geoscience data into the first neural network, determining a new residual for the new well by inputting the new geoscience data into the second neural network, and updating the predicted new performance data using the new residual.

Abstract: A method for determining a matrix permeability of a subsurface formation, including the steps: acquiring a core from the subsurface formation, imposing a fluid to the core until the core is saturated with the fluid, conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and determining the matrix permeability from decays of the pressure-pulses on the upstream side and downstream side, respectively.

Abstract: A method for determining maximum recoverable hydrocarbon (EMR) in a tight reservoir is disclosed. The method includes determining, based on downhole logs, a total measure of hydrocarbon amount within the tight reservoir, determining, by at least attributing fluid loss during core surfacing of the core sample to hydrocarbons, a non-recoverable measure of hydrocarbon amount within a core sample of the tight reservoir, and determining an EMR measure based on the total measure of hydrocarbon amount and the non-recoverable measure of hydrocarbon amount, wherein during the core surfacing pore pressure reduces from a reservoir condition to a surface condition.

Abstract: A method for determining SRV and EUR includes: monitoring an amount and a density of a hydrocarbon fluid produced from the production well; obtaining a cumulative amount of the fluid that has accumulated from a beginning of production; obtaining a relationship between the cumulative amount and a square root of the time; determining a deviation point where the relationship changes from linear to non-linear; determining a deviation amount of the fluid corresponding to the deviation point; determining a first density of the hydrocarbon fluid at the beginning of production, a second density at a pore pressure equal to a bottom hole pressure in the production well, a first porosity at the beginning of production, and a second porosity for a pore pressure equal to the bottom hole pressure; and determining SRV and the EUR based on the deviation amount, the first and second densities, and the first and second porosities.

Abstract: A method for predicting well production is disclosed. The method includes obtaining a training data set for a machine learning (ML) model that generates predicted well production data based on observed data of interest, generating multiple sets of initial guesses of model parameters of the ML model, using an ML algorithm applied to the training data set to generate multiple individually trained ML models based the multiple sets of initial model parameters, comparing a validation data set and respective predicted well production data of the individually trained ML models to generate a ranking, selecting top-ranked individually trained ML models based on the ranking, using the data of interest as input to the top-ranked individually trained ML models to generate a set of individual predicted well production data, and generating a final predicted well production data based on the set of individual predicted well production data.

Abstract: A method for determining a rock property includes positioning a core sample in a core sample assembly that is enclosed in a pressurized container with a flow inlet, a flow outlet, and a pressurized fluid inlet fluidly coupled to a pressurized fluid reservoir that includes a pressurized fluid pump; sequentially performing at least three test operations on the core sample; at each of the at least three test operations, measuring an inlet pressure at the flow inlet, measuring an outlet pressure at the flow outlet, and measuring a confining pressure within the pressurized container; and determining a permeability of the core sample based at least in part on at least one of the measured inlet pressures, at least one of the measured outlet pressures, and at least one of the measured confining pressures.

Abstract: A method for determining a rock property includes positioning a core sample in a core sample assembly that is enclosed in a pressurized container with a flow inlet, a flow outlet, and a pressurized fluid inlet fluidly coupled to a pressurized fluid reservoir that includes a pressurized fluid pump; sequentially performing at least three test operations on the core sample; at each of the at least three test operations, measuring an inlet pressure at the flow inlet, measuring an outlet pressure at the flow outlet, and measuring a confining pressure within the pressurized container; and determining a permeability of the core sample based at least in part on at least one of the measured inlet pressures, at least one of the measured outlet pressures, and at least one of the measured confining pressures.

Abstract: Systems, methods, and apparatus for determining permeability of subsurface formations are provided. In one aspect, a method includes: positioning a sample of the subsurface formation in a measurement cell, fluidly connecting an inlet and an outlet of the sample to an upstream reservoir and a downstream reservoir, respectively, flowing a fluid through the sample from the upstream reservoir to the downstream reservoir, measuring changes of an upstream pressure associated with the upstream reservoir and a downstream pressure associated with the downstream reservoir in a measurement time period, and determining a matrix permeability of the subsurface formation based on measurement data before the upstream pressure and the downstream pressure merge at a merging time point.

Abstract: A method for determining stress-dependent permeability includes providing a core sample in a pressurized core container of a testing apparatus and generating a steady-state flow of gas from an upstream reservoir in the testing apparatus along an axial direction through the pressurized core container into a downstream reservoir in the testing apparatus. During the steady-state flow, an inlet pressure at an inlet to the core sample, an outlet pressure at an outlet of the core sample, and a midpoint pressure at a midpoint of the core sample are measured. The stress-dependent permeability is calculated from a flow rate of the gas through the core sample and the measurements of the inlet pressure, the outlet pressure, and the midpoint pressure.