Technology Summary

Overview

This final issue of Journal of Canadian Petroleum Technology offers a total of 14 papers that reflect current interest in various areas of the oil and gas industry. The topics covered include heavy oil and enhanced oil recovery, steam-assisted-gravity-drainage processes, hydraulic fracturing, and reservoir simulation. A brief overview of each paper is presented. This issue also includes a listing of the winners of the SPE Outstanding Technical Editor Award and the A Peer Apart award, as presented at the 2015 SPE Annual Technical Conference and Exhibition, and a thank you to the reviewers who have volunteered their time over the past year to the peer-review process. SPE would like to take this opportunity to extend our sincere appreciation to the authors and reviewers of JCPT—past and present—for their dedication and contributions to the journal… thank you.

 

Heavy Oil and Enhanced Oil Recovery

Field-Scale Deformation Analysis of Cyclic Solvent Stimulation in Thin Unconsolidated Heavy-Oil Reservoirs With Developed Wormhole Network addresses the steps to construct a 3D mechanical Earth model to understand the contribution of production schedule on stress changes during post-cold heavy-oil production with sand (CHOPS) enhanced-oil-recovery applications in a history-matched CHOPS field in Alberta. The growing nature of the wormhole network because of sand production and the nonequilibrium foamy oil behaviour are introduced into the hydro-geomechanical model and the coupling effects on fluid production are discussed. The field-wide deformation and stress changes are analyzed in deep overburden, caprock, and reservoir to show the influence of local stress orientations in soft and stiff layers. The hydro-geomechanical model is then used for field-development planning, reservoir management, and assessment of near-wellbore regions during cyclic injection and production.

 

Oil Recovery From Gas-Over-Bitumen Reservoirs: Results From the AIDROH Pilot Project in Alberta discusses the innovative and successful implementation of air-injection technology to produce oil from bitumen reservoirs overlain by gas caps. The bitumen zone is heated be means of thermal conduction by the in-situ combustion of the residual bitumen present in the gas cap, and oil is produced by a horizontal well. The paper provides details on the components and operation of the pilot, as well as analyses of the gathered data such as observation-well temperatures, composition of the produced gas, post-burn core, and temperature along the horizontal production well. The reservoir-simulation work performed to reconcile the observed results is also summarized.

 

Successful Application of Hot-Water Circulation in the Pelican Lake Field: Results and Analyses of the E29 Hot-Water-Injection Pilot discusses the innovative and successful implementation of hot-water circulation to continuously stimulate a horizontal heavy-oil production well, which is part of a hot-waterflooding pilot. The oil around the producer is heated by means of thermal conduction by the circulation of hot water inside the wellbore through an insulated coiled tubing. The paper provides details on the components and operation of the pilot, as well as analytical analyses performed to understand the performance. The reservoir-simulation work carried out to history match its behaviour and perform forecasts is also summarized.

 

Supported Catalyst Regeneration and Reuse for Upgrading of Athabasca Bitumen in Conjunction With In-Situ Combustion discusses the successful regeneration and reuse of supported catalysts. A major expenditure in the refinery is the cost of the catalyst. The successful regeneration of the catalyst provides the refinery extra financial advantage because the catalyst expenditure is reduced. Description of the upgrading processes that use the regenerated catalyst and the generation of the spent catalysts are highlighted. A summary of the analysis of the produced oil obtained with the regenerated and the original catalysts are presented comparatively.

 

Steam-Assisted-Gravity-Drainage Processes

SAGD Well-Pair Completion Optimization Using Scab Liner and Steam Splitters discusses the methodology of scab-liner and steam-splitters design. A coupled reservoir and wellbore hydraulic-simulation study was conducted to investigate how wellbore completions can improve bitumen production. An example was provided to demonstrate the way scab liner and steam splitters changed pressure profiles inside an injector and a producer, resulting in higher bitumen-production rate. On the basis of better understanding of mechanisms, a generic guideline was proposed to match desired pressure profiles by use of different combinations of scab liners and steam splitters to match different types of reservoirs.

 

Geotechnical Characterization of Clearwater Clay Shale and Comparison of the Properties With Other Cretaceous Clay Shales in North America discusses the way in which Clearwater clay shale from the Clearwater formation in northeast Alberta forms a key element in the assessment of caprock integrity for steam-assisted-gravity-drainage projects. Geotechnical characterization of Clearwater clay shale and a comparison of its properties with other Cretaceous-aged clay shales in North America is used to define a range of representative geomechanical and constitutive model parameters relevant to numerical-simulation studies of caprock integrity.  In particular, a work flow to extract modified Cam clay constitutive model parameters from these data is presented and discussed. Determination of the critical state line, yield surface, and limit-state curve is documented, along with the development of the complete state-boundary-surface space, with attention on the transition from elastic to plastic behaviour.

 

The Effect of Clay Type on Steam-Assisted-Gravity-Drainage Performance examines the influence of two different clay types—kaolinite and a mixture of kaolinite and illite—on the sweep efficiency and oil recovery during steam-assisted gravity drainage. This is achieved by inspection of produced water, produced oil, and spent rock by use of scanning electron microscope/energy-dispersive X-ray spectroscopy and X-ray diffraction for elemental and structural analyses and contact-angle, particle-size, zeta-potential, and interfacial-tension measurements for wettability and steam/bitumen/clay interaction analysis. The asphaltene/clay/water interactions in both produced oil and residual oil are also discussed. The asphaltenes are extracted by use of a standard ASTM method, while the water and clay content in asphaltenes are determined with a thermal method and filtration process, respectively.

 

Initial Sampling of Ensemble for Steam-Assisted-Gravity-Drainage-Reservoir History Matching discusses a novel sampling method that is based on the probability-distance-minimization method to generate an initial ensemble of reduced size. The method considers multiple static measurements and geological properties and uses Kantorovich distance to quantify the probability distance between the original ensemble and the reduced ensemble, which is later optimized by use of the mixed-integer linear-optimization (MILP) technique. History matching of an SAGD reservoir using the smaller size initial ensemble derived from the proposed method and compared with the original ensemble is used to demonstrate the effectiveness of the method. The ensemble Kalman filter (EnKF) is chosen for history matching because of its ability to assimilate data for large-scale nonlinear systems. Results are compared with other methods, including importance sampling, kernel K-means clustering, and sampling by use of orthogonal ensemble members. The robustness and usefulness of each method for generating an improved initial ensemble of reduced size are analyzed and conclusions are presented.

 

Hydraulic Fracturing

Investigating the Effect of Improved Fracture Conductivity on Production Performance of Hydraulically Fractured Wells: Field Case Studies and Numerical Simulations discusses the effect of fracture conductivity on production and how to apply numerical techniques to simulate hydraulically fractured horizontal wells. A description of reservoir and fracture characterization is outlined. A new unstructured gridding approach, which handles nonorthogonal, low-angle intersections of extensively clustered fractures with nonuniform aperture distributions is highlighted. Well-treatment design and rock and fracture properties are summarized. Preparation of numerical models and interpretation of simulation results are discussed.

 

Natural-Fracture Reactivation in Shale Gas Reservoir and Resulting Microseismicity presents a successful coupling between geomechanical flow and fluid flow to simulate fracture reactivation in shale gas reservoirs. The study also predicts resulting microseismic events that are within the observed magnitude ranges. The coupling approach, connected with detailed mesh systems and innovative fracture-behaviour treatment results in a unique approach to solve these complicated phenomena. The complex subsurface settings are effectively simulated by use of near-realistic fracture-network grid models.

 

Numerical Modelling of Hydraulic Fracturing in Cohesionless Sand: Validation Against Laboratory Experiments introduces a new numerical-hydraulic-fracture model in which the smeared approach has been implemented within the continuum-mechanics framework for simultaneous simulation of shear and tensile fractures. The model is applicable to weak sandstone formations that are distinguished with high permeability and low shear strength. Phenomena such as tensile and shear band development and tensile and shear enhanced permeability are of paramount importance during hydraulic fracturing of cohesionless sand or weak sandstones, which make the fracturing response quite different from what is conventionally believed to occur in competent rocks. In the proposed model, both matrix and fracture flows have been considered, and tensile- and shear-fracture development and the respective fluid-flow processes were simulated. The smeared-fracture model is validated against a large-scale laboratory hydraulic-fracture experiment with reasonable agreement. It is shown that shear fracturing and the shear-permeability evolution are the most important mechanisms that influence and control the fracturing response of cohesionless sand. The dominant fracturing mechanism is found to be governed by the high permeability and low shear strength of the material.

Reservoir Simulation

Reservoir Characterization and History Matching of the Horn River Shale: An Integrated Geoscience and Reservoir-Simulation Approach describes a practical and systematic approach to integrating geoscience and dynamic reservoir modelling. This work starts with developing a 3D geoscience static model that is based on the sequence stratigraphic approach. The study also incorporates hydraulic conductivity of induced and natural fractures by means of measurements from shale core plugs. Building on both data sets, the study then transitions into a dynamic reservoir model that uses surveillance data, wellhead surface-pressure data, well-test data, and analytical rate-transient analysis. In addition, different techniques are presented along with a work flow to simplify and speed up the history-matching process of a multiwall pad model, at the same time addressing the difficulties and challenges in replicating the actual production behaviour. The result is a reliable numerical-simulation model that can be used to optimize the drilling and completion of future wells in the area.

 

An Approximate Semianalytical Multiphase Forecasting Method for Multifractured Tight Light-Oil Wells With Complex Fracture Geometry discusses the development of a new method for forecasting low-permeability black-oil wells that exhibit two-phase flow of oil and gas in the reservoir during the transient-linear- and boundary-dominated-flow periods. The linear-to-boundary and enhanced-fracture-region conceptual models are used in the new model development. Simulated cases are used to illustrate the accuracy of the new approach, and field cases are used to demonstrate practical applicability. The method is simpler to apply than numerical-reservoir simulation, yet yields similar forecasts in the cases studied.

 

Impact of Distance-of-Investigation Calculations on Rate-Transient Analysis of Unconventional Gas and Light-Oil Reservoirs: New Formulations for Linear Flow discusses the analytical development of distance-of-investigation (DOI) equations for the case of transient linear flow under constant-flowing-pressure and -rate conditions. For the case of constant-flowing pressure, the constant in the DOI equation, derived using two different analytical approaches, is significantly different than that previously provided, resulting in significant differences in the derived linear-flow parameter (xfk) from transient-linear-flow data. Simulated cases are used to demonstrate the accuracy of the new DOI equations, and a field case is provided to demonstrate the practical applicability.