Relative permeability (kr) functions are among the essential data required for the simulation of multiphase flow in hydrocarbon reservoirs. These functions can be measured in the laboratory using different techniques including the steady state displacement technique. However, relative permeability measurement of shale rocks is extremely difficult mainly because of the low/ultralow matrix permeability and porosity, dominant capillary pressure and stress-dependent permeability of these formations.
In this study, the impacts of stress and capillary end effects (CEE) on the measured relative permeability data were investigated. The steady state relative permeability (SS-kr) measurements were performed on Eagle Ford and Pierre shale samples. To overcome the difficulties regarding the kr measurements of shale rocks, a special setup equipped with a high-pressure visual separator (with an accuracy of 0.07 cc) was used. The kr data were measured at different total injection rates and liquid gas ratios (LGR). In addition, to evaluate the impacts of effective stress, the kr data of an Eagle Ford shale sample were measured at two different effective stresses of 1000 and 3000 psi.
From the experimental data, it was observed that the measured SS-kr data of the shale samples have been influenced by the capillary end effects as the data showed significant variation when measured at different injection rates (with the same LGR). This suggested that the liquid hold-up (i.e. capillary end effects) depends on the competition of capillary and viscous forces. In addition, it was shown that it is more necessary to correct the experimental kr data measured at the lower LGRs. Furthermore, different relative permeability curves were obtained when the kr data were measured at different effective stresses. This behavior was explained as the capillary pressure was expected to be more dominant at the higher effective stress.
The results from this study improve our understanding of unconventional mechanisms in shale reservoirs. It is evident that the behavior of unconventional reservoirs can be better predicted when more reliable and accurate relative permeability data are available. The outcomes of this study will be useful for accurate determination of such kr data.
The reporting of potential resources is essential to assess the future development plan and profitability of a petroleum discovery, but if the project is under appraised and production data are absent, analysts often use analogs for preliminary estimates of technically recoverable volumes. To address this, a workflow is presented for selecting appropriate analogs for unconventional plays and using them to estimate the target play's potential. The proposed technique is demonstrated with a case study of the as-yet undeveloped Bowland Shale, which is the most prominent of the shale plays in the United Kingdom (UK) and is at the early stage of its assessment. The paper describes the current shale gas activity in the UK, highlighting the enviromental constraints placed on would-be Bowland Shale developers, which impact on drilling and production operations and stem from the geographic proximity of urban developments, infrastructure and nature, which limit the size of well pad footprint in the UK where land use is high. Studies have estimated the play's in-place resources for possible future development, but there are few estimates of its corresponding recoverable volumes due to lack of production history. At the outset, a database is created with published minimum-average-maximum ranges of key parameters such as total organic carbon, maturity level, gas filled porosity, permeability, etc. that play a major role in resources estimation and recovery potential for all unconventional plays. A comparison of triangular distributions, key parameter by key parameter, between the target shale play and the analog database, is then carried out using novel graphical and statistical methods to establish a "confidence factor" relating to the analog's viability. The most appropriate analog for the Bowland Shale is chosen from an exhaustive list of North American shale gas plays. Analytical approaches are then used to transform a model of the published type well performance of the selected analog by exchanging key model parameters with those of the target shale play. The paper shows how UK operational constraints can be statistically incorporated into the workflow and have a marked effect on the estimated recovery from the Bowland Shale.
Fluid storage capacity measurements of core-plugs in the laboratory considers pore-volume as a function of effective stress. The latter is equal to (Applied Confining Pressure) − (Effective Stress Coefficient) x (Applied Pore Pressure). However, results are often reported as a function of difference in the applied pressures, because the coefficient is unknown and depends on the sample. This creates confusion during the interpretation of laboratory data and leads to added uncertainties in the analysis of storage capacity.
In this paper we present a new laboratory method that allows simultaneous prediction of the sample pore volume, coefficient of isothermal pore compressibility, and the stress coefficient. These quantities are necessary to predict the fluid storage as a function of effective stress. The method requires two stages of gas (helium) uptake by the sample under confining pressure and pore pressure and measures pressure-volume data. Confining pressure is always kept larger than the equilibrium pore-pressure but their values at each stage are changed arbitrarily. The method considers gas leakage adjustments at high pore pressure. The analysis is simple and includes simultaneous solutions of two algebraic equations including the measured pressure-volume data.
The model is validated by taking the reference pore volume near zero stress. The reference volume predicted matches with that measured independently using the standard helium porosimeter. For sandstone and shale, the pore compressibility is on average 10-5 psi-1 and the effective stress coefficient is slightly higher than 1. The effective stress coefficient in isotropic elastic porous materials is known as the Biot coefficient and the value we predict indicates the relationship between the bulk and grain volume moduli.
Interestingly the effective stress coefficient predicted using shale samples rich in clays and organic matter is slightly higher than for sandstone. This indicates that other features of the sample such as fine-scale texture (laminations, and anisotropy, etc.) could come into play during the fluid storage measurements.
Some of the trends and issues related to water management for tight oil and gas are discussed, including environmental, sustainability, and legislative issues associated with water handling for hydraulic fracturing. Some of the trends and issues related to water management for tight oil and gas are discussed, including environmental, sustainability, and legislative issues associated with water handling for hydraulic fracturing.
Management of produced water is driving subtle yet potentially consequential changes in certain regions. By assessing these common elements, partial risk profiles for both conditions can be assessed. Reusing produced water is becoming increasingly economic, available, and necessary. These four steps will guide operators to evaluate the viability of their options. Some of the trends and issues related to water management for tight oil and gas are discussed, including environmental, sustainability, and legislative issues associated with water handling for hydraulic fracturing.
UK's First Carbon Capture and Storage Project Could Be Operational by Mid-2020s The Acorn Project will capture about 200,000 tonnes of carbon dioxide from the St. Fergus Gas Terminal and transport it for storage to one of three depleted gas fields using existing pipelines. Levels of stress and mental health problems among UK workers are at a 17-year high, according to the latest injury and ill health statistics published by the Health and Safety Executive. The UK’s offshore oil and gas industry continued to see improvement across a broad range of health and safety indicators last year, according to a key insight published by Oil & Gas UK. Offshore Industry Has Come'Perilously Close to Disaster,' Warns UK's Health and Safety Executive The Health and Safety Executive (HSE) has warned the UK’s offshore oil and gas operators that they must do more to tackle hydrocarbon releases in the North Sea after coming “perilously close to disaster” in recent years. Oil & Gas UK recently published guidelines with its most up-to-date information aimed at helping operators ensure they have the required financial measurements in place to meet the cost of cleanup for an oil release. North Sea oil and gas production was up but greenhouse gas emissions in 2016 were down against 2015 performance, according to Oil & Gas UK’s Environment Report.
The effects of adding iron oxide NPs on the rheological and filtration properties of aqueous bentonite suspensions have been studied by several researchers. This paper presents an investigation into the effect of catalytic nanoparticles on the efficiency of recovery from continuous steam injection. A number of ongoing industry research projects are developing nanoparticles that work at the reservoir level and for fluid treatment. Though they may be a few years away from finalization, these efforts highlight nanotechnology’s increasingly sophisticated and growing application scope. This work focuses on the laboratory techniques for developing, assessing, and analyzing innovative water-based drilling fluids containing iron oxide (Fe2O3) and silica (SiO2) nanoparticles.
The technical challenges imposed by tight well spacing and fracture interactions have become a focal point of recent earnings calls between investors and the leaders of several shale producers. The picture of the future is becoming clearer, and there are fewer oil wells in it. By measuring which tests best predicted the fractures observed at the Hydraulic Fracturing Test Site, Laredo Petroleum developed a method it hopes will improve fracture modeling in other places. A close look at hundreds of feet of fractured core samples suggest that new fracture models are needed to simulate complicated reality.
Past experiences with problematic situations often drive the decision-making process, and while experience may be helpful, it can also lead to the development of biases that hamper an organization’s ability to manage dynamic environments such as unconventional projects. The application of lessons learned in projects is generally a trusted approach to tackling design challenges. However, the design of onshore production systems for unconventional resources does not allow for straightforward crossover from onshore or offshore conventional to unconventional systems. Unconventional resources are often in good supply, but difficult and expensive to develop. To develop unconventional resources, technologies like hydraulic fracturing and horizontal drilling are key, and higher oil prices will help.