We perform ab initio self-consistent Green's function calculations of the closed shell nuclei 4 He, 16 O, and 40 Ca, based on two-nucleon potentials derived from lattice QCD simulations, in the flavor SU(3) limit and at the pseudoscalar meson mass of 469 MeV/c 2 . The nucleon-nucleon interaction is obtained using the hadronsto-atomic-nuclei-from-lattice (HAL) QCD method, and its short-distance repulsion is treated by means of ladder resummations outside the model space. Our results show that this approach diagonalizes ultraviolet degrees of freedom correctly. Therefore, ground-state energies can be obtained from infrared extrapolations even for the relatively hard potentials of HAL QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total binding energies are sensibly improved by the full account of many-body correlations. The results suggest an interesting possible behavior in which nuclei are unbound at very large pion masses and islands of stability appear at first around the traditional doubly magic numbers when the pion mass is lowered toward its physical value. The calculated one-nucleon spectral distributions are qualitatively close to those of real nuclei even for the pseudoscalar meson mass considered here.

We discuss recent ab initio calculations based on self-consistent Green's function theory. It is found that a simple extension of the formalism to account for two-nucleon scattering outside the model space allows to calculate non-soft interactions. With this, it is possible to make predictions for Lattice QCD potentials, obtained so far at pion masses of m π = 0.47 GeV/c 2 . More traditional calculations that use saturating chiral EFT forces yield a good description of nuclear responses and nucleon knockout spectroscopy.

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Evidence continues to mount to indicate that the geometric placement of fracture stages and perforation clusters in horizontal wells results in variable well production, with many clusters contributing little or no production. Any engineered completion design should require stages to be segregated by similar petrophysical and mechanical properties. The authors propose to reduce the cost per barrel of oil equivalent (BOE) and to improve estimated ultimate recovery (EUR) by using a novel log-derived completion method to better select perforation clusters and stage location to provide better fracture placement. A low-risk, pumped down, cased-hole pulsed-neutron log (PNL) is used after the well is cemented before completion. Using readily available geosteering software, the geologic projection of vertical well log measurements and the interpreted formation properties along the horizontal well enable a rigorous calibration method for PNL interpretation. Inelastic pseudodensity, neutron porosity, and resistivity-sigma calibrations can then generate a cased-hole triple combo. Elemental yields for silica, calcite, and potassium are used with additional clay inputs for a basic mineralogy interpretation. These inputs, within a specialized workflow, calculate a “production index” and “frac index” used to generate custom staging designs. Experience in a major unconventional play has shown a dramatic reduction in the number of stages and the completion cost per well. In addition, data from producing wells, using a software-derived stimulation design, has been matched to geometrically staged wells in the area. The addition of PNL data to interpret the position of the lateral well has been observed to reduce uncertainty when compared to the logging while drilling (LWD) gamma ray (GR) alone. The completion results for stages also provide good evidence that the overall efficacy of the stimulation treatment was increased by the perforation placement. The conclusions from this work show substantial completions cost savings per well while maintaining overall EUR in a difficult unconventional shale play. Based on pressure observations during stimulation, it is believed that stimulation efficiency has been increased. Using fewer stages to target the more productive rock and perforation clusters to target the sweet spots for stimulation has provided a substantial cost/BOE reduction. Although the technology for using a PNL log in the horizontal well has been attempted previously, there was not the benefit of a rigorous calibration method. The geologic projection of vertical wells is a novel approach to calibrate thousands of feet of logged PNL data. In addition, the custom staging design uses a novel, unbiased approach to select the optimum stage and perforation placement to minimize completions cost while maximizing productivity.

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