Post-stack 3D seismic data is spatially blurred by the effect of migration operators with limited aperture widths, which is not conducive to discontinuity (such as fault, channel, etc.) detection. By approximating the migration blur with a time-invariant point spread function (PSF), seismic image deblurring method has been used to obtain a deblurred seismic data with enhanced discontinuity. We denote this method as TIPSF. By applying a discontinuity detection method (say, the coherence algorithm) on the deblurred seismic data, a better result is achieved, in comparison with the result obtained by applying the same method on the original seismic data directly. Since the migration blurs are always time-dependent in real seismic data, we propose a time-variant PSF estimation algorithm for seismic image deblurring in this paper, which is named as TVPSF. In which, we first obtain a series of initial PSFs' estimates from a 3D seismic data by estimating one PSF from each horizontal time slice (HTS), respectively. Secondly, we construct a sequence of time windows with adaptive variable length, according to the similarities with these initial PSFs' estimates. Thirdly, we use the average of these initial PSFs' estimates, which are fallen in one time window, to be the final PSF estimate corresponding to the center sample point of this time window. For these non-center sample points, a linear interpolation method is used to obtain their final PSFs' estimates using the PSFs' estimates of those center sample points. At last, a 2D Wiener filter is used to perform seismic image deblurring, HTS by HTS. Furthermore, in order to adapt to different signal-to-noise ratios (SNR) level in time slices of the 3D seismic data, our proposed method adjusts the whitening factor of the Wiener filter for each HTS according to its energy. Applications of both TVPSF and TIPSF methods on a real data set show that the TVPSF method outperforms the TIPSF method clearly, which demonstrate the validity of the proposed method.
Presentation Date: Tuesday, October 18, 2016
Start Time: 1:00:00 PM
Presentation Type: ORAL
Equipment integrity and systems reliability are of paramount interest in oil and gas industry as they guarantee not only the safety of personnel working in the field but also for the protection of environmental degradation that could inadvertently occur due to unprecedented equipment failure. This paper presents a finite element analysis of the riser base that is subject to repeated loading resulting from severe slug flow in an offshore production flowline-riser (TTR) system. Commercial software packages used in this simulation study are PVTsim 20, OLGA 7 and ABAQUS 6.14-1. The typical flowline-riser pipe system was modeled with a 10 inch (0.254 m) nominal pipe size (NPS) of wall thickness 0.562 inch (0.0143 m) and of API 5L Grade X- 65 steel material. PVTsim was used to generate the PVT properties of the fluid model which is a typical heavy oil of API gravity in the range of 23-27 degrees and hence the preparation of fluid table files for the multiphase simulator. Slug tracking module in the program was used to track the severe slug development in the flowline-riser system for a typical oilfield producing at the rate of 10000 barrels of oil per day (bopd) (1584 m³/day). Pressure-time series prediction by the multiphase simulator at the riser base was used to plot the pressure amplitude loading curve in ABAQUS for the structural analysis. Numerical results from multiphase simulator shows that severe slugging occurs in the riser at that production rate and the riser base experiences the most pressure loading during the slug buildup in the riser and as well as the cyclic loading behavior of severe slugging in the riser, while that of ABAQUS implicit dynamic analysis shows the displacement mode of the structure and stress distributions in the finite element model of the riser base during the peak of the severe slugging for 5 cycles period of the severe slug flow. The results of this numerical study will provide a technical data for the enhancement of the design of a riser pipe especially the 10 inch nominal pipe size considered in this paper which has substantial application in deepwater offshore field development.
Fragoso, Alfonso (Schulich School of Engineering, University of Calgary, Canada) | Wang, Yi (Schulich School of Engineering, University of Calgary, Canada) | Jing, Guicheng (Schulich School of Engineering, University of Calgary, Canada) | Aguilera, Roberto (Schulich School of Engineering, University of Calgary, Canada)
The objective of this paper is to investigate the possibility of using gas injection to improve liquids recoveries from containers in shale condensate and shale oil reservoirs. Liquids recoveries from shales are known to be very low. A method is proposed to increase these recoveries through gas recycling and by using dry gas that is available within relatively short distances of the shale condensate and oil containers considered in this study. This dry gas is not being produced at this time due to current market conditions.
In practice, some shale reservoirs such as the Eagle Ford in the United States and the Duvernay in Canada present the challenge of unconventional fluids distribution: shallower in the structure there is black oil, deeper is condensate and even deeper is dry gas. So the fluids distribution is exactly the opposite of what occurs in conventional reservoirs. Differences in burial depth, temperature, and vitrinite reflectance are used to explain this unique distribution.
In the first case, a single porosity compositional simulation is used to investigate the possibility of improved liquid recovery from the condensate container by using dry gas injection obtained from the recycling process plus dry gas from the deeper part of the structure. Fluid properties are similar to those of the Duvernay shale.
In the second case, dual permeability compositional simulations are used to investigate practical aspects of the condensate container that can lead to improved recoveries in the Eagle Ford shale. Sensitivities are run that include bottomhole pressure (BHP), natural fracture permeability and spacing, hydraulic fracture length and spacing, and distance between parallel wells. Results from dual permeability simulations are compared with dual porosity behavior. Fluid properties are similar to those of the Eagle Ford shale.
In the third case, compositional single porosity, dual porosity and dual permeability simulations are used to study the possibility of injecting gas in the oil container. A cyclic huff and puff gas injection is also investigated. Fluids and rock properties are similar to those of the Eagle Ford shale.
The study leads to the conclusion that dry gas from deeper shales can be put to good use by injecting it into the middle and upper parts of the structure. In the middle part of the structure there is a container where gas condensate is predominant. In here, a re-cycling injection project allows to inject dry gas stripped from the condensate fluids. This is supplemented with dry gas produced from the deeper part of the structure.
In the upper part of the structure there is a container where oil is predominant. In here, injection is implemented using dry gas produced from the deeper part of the structure. Permeability plays a critical role in the case of single porosity simulations. Dual porosity and dual permeability simulations indicate that oil recovery can be enhanced significantly in naturally fractured shales. Diffusion plays a fundamental role on the performance of shale gas injection particularly in the case of naturally fractured shales. It is found that cyclic huff and puff gas injection can help increase oil recovery.
To the best of our knowledge, the idea developed in this paper that includes all fluids (oil, condensate and dry gas) present in the same shale structure within relatively short distances of each other has not been published previously in the literature.
Changrong, Bian (SINOPEC Exploration & Production Research Institute) | Wang, Yi (SINOPEC Exploration & Production Research Institute) | Feng, Xingqiang (SINOPEC Exploration & Production Research Institute) | Zhang, Yu (SINOPEC Exploration & Production Research Institute) | Li, Zhihua (GeoReservoir Research) | Shen, Feng (GeoReservoir Research)
In this study, we present an integrated approach to develop a two-scale fracture model for the Ordovician carbonate fractured reservoir in the Yubei area. The objective of this study is to provide new insights into the impact of fractures on oil production and to recommend drilling strategy. Fractures are characterized by using log data, 3D seismic attribute, borehole image logs and reservoir production data. Image logs illustrate that the dominant reservoir fractures trending in the NE direction parallel to the present-day maximum horizontal compressive stress and are consistent with the major fault system. The electrofacies generated with conventional logs are calibrated into different fracture units by using borehole image logs and reservoir dynamic data. The dynamic behavior of the complex matrix and fracture system is characterized for fracture units at wells. For layer bound diffuse fractures, the fracture properties are modeled statistically set by set with borehole image logs, fracture seismic facies volume representing degree of the fracturation and seismic geometric attribute. Fracture lineaments at the corridor scale are extracted directly from edge-enhanced seismic attribute. Fracture lineaments are cleaned and meshed to define their topology relationships to construct a comprehensive DFN (Discrete Fracture Network) model. Fracture networks are characterized deterministically, which constitute a unique fracture model on the reservoir scale. DFN model provides a geological representation how these fractures are spatially organized in the subsurface and how they may enhance or inhibit fluid flow. The final fracture model honored the two scale fracture models. Grid-cell permeability properties are derived from the two-scale fracture model. Based on the dynamic behavior of fracture units, fracture properties are calibrated against the dynamic data. Our results show that NE orientated fractures are open and conductive. The high productivity zones are characterized by high permeability located in the vicinity of faults. Enhanced oil recovery operations could be optimized using production wells oriented at high angles to NE orientated fractures.
Pipelines laid on the surface of seabed within areas of shipping movements become increasingly susceptible to risks stemming from anchor impact damages. The impact from ship anchor may lead to local deformation and fracture in the pipeline. Large-scale tests have been carried out to study the penetration depth of the anchor and the dent depth of the pipeline under the impact of a dropped anchor. This article describes the experimental study that was carried out to examine the effects from variations of soil type, pipeline embedment depth and anchor velocity regarding pipeline response. Results from the test show that the properties of soil above pipeline play an important role in impact energy dissipation, and the dent depth is sensitive to anchor velocity.
The nonlinear behavior at the pipe soil contact interface at Touchdown Zone (TDZ) is critical for global and local Steel Catenary Riser (SCR) deformations, especially the predicted fatigue life. In this paper, soft cohesive soil was chosen as the medium in view of the deepwater geotechnical conditions and a series of model tests were carried out to research the vertical pipe soil interaction. The soil resistances under different pipe model vertical moveme nt velocity were recorded during the tests, so as to research the effect of pipe movement velocity to the pipe soil interaction. And the simulation results obtained by Coupled Eulerian Lagrangian (CEL) method were compared to model test data. An empirical formula to calculation the soil resistance during vertical pipe soil interaction is established by nonlinear fitting based on numerical simulation results.
Early arrivals play an important role for Full Waveform Inversion (FWI) in most successful field data examples. However, since their propagation paths are confined to shallow part of the velocity model, it is difficult to effectively update velocity below certain depth limit. In this study, we propose a two-step strategy in FWI and apply it on the reflected waves from an ocean bottom seismic (OBS) dataset. The inversion result demonstrates that the procedure works well and the velocity model is successfully updated using the reflection energy.
Sun, Shuangwen (Center for Ocean and Climate Research, First Institute of Oceanography State Ocean Administration) | Lan, Jian (Physical Oceanography Laboratory, College of Physical and Environmental Oceanography Ocean University of China) | Wang, Yi (Physical Oceanography Laboratory, College of Physical and Environmental Oceanography Ocean University of China)