Each of these is discussed briefly in the next two sections. Thereafter--except for another section on probabilistic procedures near the end--the chapter will focus on deterministic procedures because they still are more widely used. Both procedures need the same basic data and equations. Reserves calculated using such procedures are classified subjectively on the basis of professional judgments of the uncertainty in each reserve estimate and/or of pertinent regulatory and/or corporate guidelines. Probabilistic procedures recognize that uncertainties in input data and equations to calculate reserves may be significant.
Transmitting electrical current to the subsurface can create special considerations. Successful application of electromagnetic heating often requires a multi-disciplinary approach combining electric engineering and petroleum engineering. To assist petroleum engineers considering this approach, this article identifies some of the issues that an electrical engineer might normally anticipate and address. In most practical situations, we are concerned with fields that vary periodically in time (the sinusoidal steady state generally). In these cases the electrical phenomena are properly described by Maxwell equations in terms of complex vector field intensities of electric and magnetic fields (E and H); complex vector field electric, magnetic, and current densities (D,B,J); complex charge concentrations (ρc); and complex material parameters: conductivity, permittivity, and permeability (σ, ε, μM).
Recent studies have indicated that Huff-n-Puff (HNP) gas injection has the potential to recover an additional 30-70% oil from multi-fractured horizontal wells in shale reservoirs. Nonetheless, this technique is very sensitive to production constraints and is impacted by uncertainty related to measurement quality (particularly frequency and resolution), and lack of constraining data. In this paper, a Bayesian workflow is provided to optimize the HNP process under uncertainty using a Duvernay shale well as an example.
Compositional simulations are conducted which incorporate a tuned PVT model and a set of measured cyclic injection/compaction pressure-sensitive permeability data. Markov chain Monte Carlo (McMC) is used to estimate the posterior distributions of the model uncertain variables by matching the primary production data. The McMC process is accelerated by employing an accurate proxy model (kriging) which is updated using a highly adaptive sampling algorithm. Gaussian Processes are then used to optimize the HNP control variables by maximizing the lower confidence interval (μ-σ) of cumulative oil production (after 10 years) across a fixed ensemble of uncertain variables sampled from posterior distributions.
The uncertain variable space includes several parameters representing reservoir and fracture properties. The posterior distributions for some parameters, such as primary fracture permeability and effective half-length, are narrower, while wider distributions are obtained for other parameters. The results indicate that the impact of uncertain variables on HNP performance is nonlinear. Some uncertain variables (such as molecular diffusion) that do not show strong sensitivity during the primary production strongly impact gas injection HNP performance. The results of optimization under uncertainty confirm that the lower confidence interval of cumulative oil production can be maximized by an injection time of around 1.5 months, a production time of around 2.5 months, and very short soaking times. In addition, a maximum injection rate and a flowing bottomhole pressure around the bubble point are required to ensure maximum incremental recovery. Analysis of the objective function surface highlights some other sets of production constraints with competitive results. Finally, the optimal set of production constraints, in combination with an ensemble of uncertain variables, results in a median HNP cumulative oil production that is 30% greater than that for primary production.
The application of a Bayesian framework for optimizing the HNP performance in a real shale reservoir is introduced for the first time. This work provides practical guidelines for the efficient application of advanced machine learning techniques for optimization under uncertainty, resulting in better decision making.
Yong, Wen Pin (PETRONAS Research Sdn. Bhd.) | Azahree, Ahmad Ismail (PETRONAS Research Sdn. Bhd.) | M Ali, Siti Syareena (PETRONAS Research Sdn. Bhd.) | Jaafar Azuddin, Farhana (PETRONAS Research Sdn. Bhd.) | M Amin, Sharidah (PETRONAS Research Sdn. Bhd.)
This paper presents a two-way coupled modelling approach to simulate CO2 movement and containment with geochemical reactions and geomechanical effects. CO2 storage simulation studies cover three main disciplines, reservoir engineering, geochemistry and geomechanics. This new approach of coupled modelling simulation, by simultaneously simulate both effects of geochemistry and geomechanics, is considered as a more representative and better predictive modelling practice.
The integration of geochemistry and geomechanics effects is important for CO2 sequestration modelling. There are a number of published studies on coupled modelling for CO2 storage. However, the majority of the studies has only covered dynamic-geomechanics or dynamic-geochemistry interaction, without considering any direct geomechanics-geochemistry interaction in a reservoir condition. It is crucial to understand the integrated effects when injected CO2 dissolves into formation water and interacts with formation rock. Depending on in-situ conditions, the formation water with dissolved CO2 could weak or strengthen the formation stress due to geochemical reactions of formation minerals. Therefore, coupled modelling is needed to ensure the long-term safety of CO2 containment at a CO2 storage site with the interactions among geomechanical, geochemical and dynamic fluid flow, and especially to understand the slow and not experimentally accessible mineral reactions.
In this paper, a high CO2 content gas field in Malaysia with high temperature (150°C) and high pressure (350 bar) has been studied using integrated coupled modelling approach. The simulation input parameters are first investigated and collected from literature and laboratory studies. A two-way coupled modelling simulation with the consideration of geochemistry and geomechanics effects is desirable because it allows the updates of reservoir properties back and forth in every time step. Different CO2 trapping mechanisms, long term fate analysis, subsidence and heaving analysis, and changes of porosity and permeability are investigated. The time frame of simulation studies consists of CO2 injection period (15 years) and post CO2 injection period (500 years).
During the first 15 years of CO2 injection, 95.13% of injected CO2 is structurally trapped, 3.67% of CO2 is soluted in formation water and 1.2% is trapped by mineralization. About 0.041m of heaving is observed at the injection area while about 0.05m of subsidence is observed at the production area. In the investigation of long-term CO2 fate, it is observed that CO2 gas will be trapped between the lighter hydrocarbon gas layer and aquifer due to density difference.
When the head of Libya’s state energy company visited Sharara oil field in early July, community leaders and workers crowded into a conference room to ask about jobs, training, and services for local people. Public acceptance is a major challenge for the siting of facilities. The offering of compensation to communities potentially helps to create the perception of a fairer distribution of local risks and nonlocal benefits. This may help to prevent or solve siting controversies. Anadarko Petroleum said late on 30 June that it has tested more than 4,000 active oil and gas lines and plugged another 2,400 inactive ones per a state order issued after a fatal home explosion in Firestone, Colorado, in April.
Two more oil fields in Libya are being closed after an armed group took over pipelines to both deposits, further disrupting the OPEC nation’s plan to boost crude production. Libya halted loadings from its biggest oil field in the latest disruption to the nation’s crude production and shipments. Libya’s biggest oil field, Sharara, is “back to normal” after a disruption caused by protests in the politically fragmented country, the state National Oil Corp. (NOC) said.
Oil production at Libya’s Sharara field, the country’s largest, was resuming on 6 September after a valve was reopened on a pipeline shut by an armed group for more than 2 weeks, Libyan oil industry sources said. When the head of Libya’s state energy company visited Sharara oil field in early July, community leaders and workers crowded into a conference room to ask about jobs, training, and services for local people. Libya’s oil production has plunged by almost a quarter after workers shut the OPEC country’s biggest field to protest lack of medical care following the death of a colleague, a person familiar with the matter said.
Just as Libya resumes oil exports from recently shuttered ports, an attack on its largest field is setting back progress yet again. Oil production at Libya’s Sharara field, the country’s largest, was resuming on 6 September after a valve was reopened on a pipeline shut by an armed group for more than 2 weeks, Libyan oil industry sources said. Two more oil fields in Libya are being closed after an armed group took over pipelines to both deposits, further disrupting the OPEC nation’s plan to boost crude production. Libya halted loadings from its biggest oil field in the latest disruption to the nation’s crude production and shipments. Libya’s biggest oil field, Sharara, is “back to normal” after a disruption caused by protests in the politically fragmented country, the state National Oil Corp. (NOC) said.
Anadarko Petroleum wants a fleet of at least six vehicles with armor heavy enough to stop AK-47 bullets at its natural-gas project in Mozambique. And it needs them soon. By examining two very different security-risk environments, this paper will illustrate how easily security-related human-rights risks can go unnoticed unless care is taken early in the risk-management process. Oil production at Libya’s Sharara field, the country’s largest, was resuming on 6 September after a valve was reopened on a pipeline shut by an armed group for more than 2 weeks, Libyan oil industry sources said. A third Damen security vessel will be deployed to provide security and other support services to the international offshore oil companies active off the coast of Nigeria in the Gulf of Guinea, in cooperation with the Nigerian Navy.
The F field in the Middle East currently has more than 40 producing wells in the center of the structure. The uneven well distribution limits the understanding of 3D reservoir characterization, particularly in the flank areas. A new technique that analyzes scanning electron microscope (SEM) images of formation samples has been used to measure porosity and total organic carbon (TOC) in the Wolfcamp Shale of the Delaware Basin in west Texas.