Pressure-Transient Behavior of Partially Penetrating Inclined Fractures With a Finite Conductivity

Summary Field studies have shown that, if an inclined fracture has a significant inclination angle from the vertical direction or the fracture has a poor growth along the inclined direction, this fracture probably cannot fully penetrate the formation, resulting in a partially penetrating inclined fracture (PPIF) in these formations. It is necessary for the petroleum industry to conduct a pressure-transient analysis on such fractures to properly understand the major mechanisms governing the oil production from them. In this work, we develop a semianalytical model to characterize the pressure-transient behavior of a finite-conductivity PPIF. We discretize the fracture into small panels, and each of these panels is treated as a plane source. The fluid flow in the fracture system is numerically characterized with a finite-difference method, whereas the fluid flow in the matrix system is analytically characterized on the basis of the Green's-function method. As such, a semianalytical model for characterizing the transient-flow behavior of a PPIF can be readily constructed by coupling the transient flow in the fracture and that in the matrix. With the aid of the proposed model, we conduct a detailed study on the transient-flow behavior of the PPIFs. Our calculation results show that a PPIF with a finite conductivity in a bounded reservoir can exhibit the following flow regimes: wellbore afterflow, fracture radial flow, bilinear flow, inclined-formation linear flow, vertical elliptical flow, vertical pseudoradial flow, inclined pseudoradial flow, horizontal-formation linear flow, horizontal elliptical flow, horizontal pseudoradial flow, and boundary-dominated flow. A negative-slope period can appear on the pressure-derivative curve, which is attributed to a converging flow near the wellbore. Even with a small dimensionless fracture conductivity, a PPIF can exhibit a horizontal-formation linear flow. In addition to PPIFs, the proposed model also can be used to simulate the pressure-transient behavior of fully penetrating vertical fractures (FPVFs), partially penetrating vertical fractures (PPVFs), fully penetrating inclined fractures (FPIFs), and horizontal fractures (HFs).

Chiral Magnetic Effect Search in p(d)+Au, Au+Au Collisions at RHIC

The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field of single-handed quarks, caused by interactions with topological gluon fields from QCD vacuum fluctuations. A major background of CME measurements in heavy-ion collisions comes from resonance decays coupled with elliptical flow anisotropy. These proceedings present two new studies from STAR to shed further light on the background issue: (1) small system p+Au and d+Au collisions where the CME signal is not expected, and (2) pair invariant mass dependence where resonance peaks can be identified.

On the rapidity distribution of nucleons participating in elliptical flow at intermediate energies

The distribution of nucleons participating in elliptical flow is studied for the reactions of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] using isospin-dependent quantum molecular dynamics (IQMD) model for various centrality ranges and over the wide range of intermediate energy. Our findings reveal that the sigma (width) of rapidity distribution obtained varies with mass of colliding system at a given energy. The peak of rapidity distribution decreases with decrease in the mass of colliding nuclei. Transition energy as well as width of rapidity distribution depends on the mass of fragment for a given centrality. Influence of isospin dependent symmetry energy and nucleon–nucleon cross-section can be studied using rapidity distribution. Second transition energy depends on the mass of the fragment. Rotational phenomenon of nucleons can be observed for nucleons participating in elliptical flow.