Crude Oil Operations Research Articles

Heuristic rescheduling of crude oil operations to manage abnormal supply chain events

AbstractGlobalization and the resultant complexity of today's supply chains require that enterprises be agile and proactive. This communication looks at a refinery supply chain where disruptions such as crude arrival delay could make the current schedule infeasible and necessitate rescheduling of operations. Existing approaches for generating (near) optimal schedules for a real‐world refinery typically require significantly large amounts of time. This is undesirable when rectification decisions need to be made in a short time. Further, when the problem data given to the existing scheduling approaches are changed, as is the case during a disruption, the optimizers follow different solution paths and result in substantially different schedules. A heuristic rescheduling strategy is proposed that overcomes both these shortcomings. The key insight exploited here is that any schedule can be broken into operation blocks. Rescheduling is performed by modifying these blocks in the original schedule using simple heuristics to generate a new schedule that is feasible for the new problem data. Our strategy avoids major operational changes by preserving—as far as possible—the blocks in the original schedule. The major advantages of the proposed method are its real‐time computational performance and the minimal changes to the operations as compared to total rescheduling. Further, the proposed strategy can also identify many feasible schedules and allow refinery personnel to select one by considering other factors that cannot be adequately modeled in a scheduler. Our method is illustrated using five types of disruptions occurring in a refinery. The various factors that affect the robustness of a supply chain in the face of disruptions are also discussed. © 2007 American Institute of Chemical Engineers AIChE J, 2007.

Novel solution approach for optimizing crude oil operations

AbstractScheduling of crude oil operations is a complex nonlinear problem, especially when tanks hold crude mixes. We present a new mixed‐integer nonlinear programming (MINLP) formulation and a novel, mixed‐integer linear programming (MILP)–based solution approach for optimizing crude oil unloading, storage, and processing operations in a multi‐CDU (crude distillation unit) refinery receiving crude from multiparcel VLCCs (very large crude carriers) through a high‐volume, single‐buoy mooring (SBM) pipeline and/or single‐parcel tankers through multiple jetties. Mimicking a continuous‐time formulation, our primarily discrete‐time model allows multiple sequential crude transfers to occur within a time slot. It incorporates several real‐life operational features including brine settling and tank‐to‐tank transfers, and is superior to other reported models. Notably our algorithm avoids concentration discrepancy and MINLP solutions by identifying a part of the horizon, for which its linear relaxation is exact, and then solving this MILP repeatedly with progressively shorter horizons. By using 8 h time slots and a hybrid time representation, an attractive approach to this difficult problem is presented.© 2004 American Institute of Chemical Engineers AIChE J, 50:1177–1197, 2004

A new continuous-time formulation for scheduling crude oil operations

In today's competitive business climate characterized by uncertain oil markets, responding effectively and speedily to market forces, while maintaining reliable operations, is crucial to a refinery's bottom line. Optimal crude oil scheduling enables cost reduction by using cheaper crudes intelligently, minimizing crude changeovers, and avoiding ship demurrage. So far, only discrete-time formulations have stood up to the challenge of this important, nonlinear problem. A continuous-time formulation would portend numerous advantages, however, existing work in this area has just begun to scratch the surface. In this paper, we present the first complete continuous-time mixed integer linear programming (MILP) formulation for the short-term scheduling of operations in a refinery that receives crude from very large crude carriers via a high-volume single buoy mooring pipeline. This novel formulation accounts for real-world operational practices. We use an iterative algorithm to eliminate the crude composition discrepancy that has proven to be the Achilles heel for existing formulations. While it does not guarantee global optimality, the algorithm needs only MILP solutions and obtains excellent maximum-profit schedules for industrial problems with up to 7 days of scheduling horizon. We also report the first comparison of discrete- vs. continuous-time formulations for this complex problem.

Refinery Short-Term Scheduling Using Continuous Time Formulation: Crude-Oil Operations

This paper addresses the problem of crude-oil short-term scheduling, which is the first part of the overall refining operations. The problem involves the optimal operation of crude-oil unloading from vessels, its transfer to storage tanks, and the charging schedule for each crude-oil mixture to the distillation units. A novel model is developed based on a continuous-time representation and results in a mixed-integer linear programming (MILP) problem. The state-task network representation is used throughout this paper. The proposed formulation is applied to several case studies and leads to fewer binary and continuous variables and fewer constraints compared with existing discrete-time models. Thus, an efficient solution can be achieved using available MILP solvers.

A Systematic Method to Predict Cloud Point Temperature and Solid Precipitation

Solid precipitations (or depositions) in crude oil operations are undesirable because they may eventually plug the process equipment and/or pipelines; as such, accurate prediction of cloud point temperature is essential in the design and operation of many oil production facilities. Determining the cloud point temperature of a mixture requires a robust solution of a multiphase, multicomponent phase equilibrium problem. Solution of the phase equilibrium problem rests on the relations set by the Gibbs criterion for stable equilibrium and the principle of mass conservation. Mathematically, two solution methods are used to characterize the equilibrium properties of a mixture at given temperature and pressure: the equal-fugacity (iteration-function formulation) and the Gibbs free energy minimization approach. In addition, an accurate solution model capable of predicting multiphase formation is required. In this study, we implement the iteration function method enhanced with a solid–liquid–vapor phase-check procedure to calculate cloud point temperatures and the amount of solid precipitations. The Peng-Robinson equation of state with a modified α function, as suggested by Gasem et al. ([2001]), was utilized to model vapor–liquid equilibria while regular solution theory was used to describe solid-liquid equilibria. We also present a systematic method to characterize the heavy components of oil. The results of this study are in excellent agreement with experimental cloud point temperature and solid precipitation data for four North Sea oils reported by Pedersen et al. ([1991]).

Beyond Phase I Environmental Site Assessments-conducting Business Environmental Risk Assessments Of Oil Field Acquisitions

Environmental due diligence investigations for proposed oil field acquisitions are typically conducted for two different purposes. In the first case, an oil company desires to purchase an oil field to conduct on-going crude oil and natural gas production operation. In the second case, the owner of the property (an oil company) desires to sell an existing oil field operation to a real estate developer for residential, commercial, or industrial redevelopment. The American Society of Testing Materials (ASTM) has developed a standard practice for conducting Phase I Environmental Site Assessments (Phase I Assessment) associated with the transfer of commercial property (E-1527-97). The primary objectives of the ASTM standard practice is to identify apparent conditions of environmental concern and conduct adequate due diligence so that the buyer can avail himself of the “innocent purchaser provision” under Comprehensive Emergency Response, Compensation, and Liability Act (CERCLA). These objectives have limited relevance for most acquisitions of oil field properties. Most oil field properties have environmental impairments. The threshold questions relate to the allocation of risk for current and future liabilities between the buyer and seller. There is a petroleum products exclusion under CERCLA. An Environmental Business Risk Assessment goes beyond the traditional Phase I Assessment to better meet the business needs of purchasers of oil field properties. The scope of the Environmental Business Risk Assessment is tailored to the level of sophistication and the risk tolerance of the buyer and the nature of the deal. Buyers of oil field properties can range from oil companies with environmental staffs to real estate developers who have limited knowledge of oil field operations. Sophisticated buyers may only need assistance identifying “exception” issues and estimates of the most likely cost and worst case scenario costs associated with these identified current and future liabilities. These buyers can generally estimate future well abandonment and facility demolition costs in-house. These buyers may also be able to estimate in-house remediation costs associated with shallow crude oil–impacted soil and other conditions typical of oil field operations. Less sophisticated buyers may need more assistance in these areas. For buyers interested in redevelopment of oil fields, the threshold question is can the site be prepared for redevelopment at a low enough cost in order that the developer can make a desired rate of return on their investment. One way to address this issue is through a focused Phase I/Phase II Assessment conducted in stages. The primary objective of Phase I is to gather just enough information to select locations for the focused Phase II investigation. The objective of the first stage of the Phase II Investigation is to confirm the general nature and extent of environmental impairments to ascertain whether it makes sense to continue. In some cases, this initial investigation will suggest that the cost of site remediation will exceed an economic threshold that makes redevelopment of the site unattractive. If the initial Phase II Assessment work is favorable, additional work is conducted consistent with the level of business risk and uncertainty the developer is willing to accept. Historically, oil field sellers have provided either a full or partial indemnification to the buyer for environmental conditions that existed before the date of sale or have provided a due diligence period after the date of sale for the buyer to conduct additional environmental investigations. In the later case, the buyer could make claims against the seller for environmental conditions that were discovered that had a liability above a certain dollar amount as a post-closing adjustment to the purchase price. These types of deals are less common today. More typical today is an “as-is” sale where the seller is willing to entertain adjustments in the purchase price for environmental impairments identified by the buyer in a due diligence period before closing. The Environmental Business Risk Assessment provides information the buyer needs to make informed business decisions about allocation of risk as a part of the negotiation of the Purchase and Sales Agreement.

Planning and scheduling models for refinery operations

The main objective of this work is to discuss planning and scheduling applications for refinery operations. Firstly, the development of a nonlinear planning model for refinery production is presented. The model is able to represent a general refinery topology and allows the implementation of nonlinear process models as well as blending relations. Considering the market limitations for each oil derivative usually supplied by the refinery, the optimization model is able to define new operating points, thus increasing the production of more valuable products, while satisfying all specification constraints. Real-world applications are developed for the planning of diesel production in the RPBC refinery in Cubatão (SP, Brazil) among others. The optimization results were compared to the current situation, where no computer algorithm is used and the stream allocation is made based on experience, with the aid of manual calculations. The new operating point represents an increase of several million dollars in annual profitability. The second part of the work addresses scheduling problems in oil refineries that are formulated as mixed integer optimization models and rely on both continuous and discrete time representations. The problem of crude oil inventory management that involves the optimal operation of crude oil unloading from pipelines, transfer to storage tanks and the charging schedule for each crude oil distillation unit will be discussed. Furthermore, the paper will consider the development and solution of optimization models for short-term scheduling of a set of operations that includes: product receiving from processing units, storage and inventory management in intermediate tanks, blending in order to attend oil specifications and demands, and transport sequencing in oil pipelines. Important real-world examples on refinery production and distribution are reported: the diesel distribution problem at RPBC refinery and the production problems related to the fuel oil/asphalt and LPG areas of the REVAP refinery in São José dos Campos (SP, Brazil), which produces approximately 80% of the national consumption.

A Critical Review of Cancer Epidemiology in the Petroleum Industry, with a Meta-analysis of a Combined Database of More Than 350,000 Workers

In 1989 we published a critical review of cancer epidemiology in petroleum workers, which included as a component of the review a meta-analysis by cancer site. Subsequently we have completed three additional reviews and meta-analyses on cell-type-specific leukemias (1995), multiple myeloma (1997), and non-Hodgkin's lymphoma (2000). The objective of the present investigation was to update our 1989 review and meta-analysis of nonlymphohematopoietic cancers in cohort studies of petroleum workers. Included in the present investigation were cohort studies of petroleum workers from the United States, the United Kingdom, Canada, Australia, Finland, Sweden, and Italy. Individual studies were reviewed with regard to specific cancer sites. For each cancer of interest, risk ratios from the individual studies were presented. In some studies, subcohort analyses stratified by exposure parameters such as length of employment, job category, and hire year were also reported. These subcohort or stratified analyses were reviewed and the results of these analyses were taken into consideration in our interpretation. In addition to the qualitative review of individual studies, a meta-analysis was performed to combine data from individual cohort studies of petroleum workers. The primary purpose of the meta-analysis was to provide a summary measure of risk for each cancer site. Based on a review and meta-analyses of cohort studies of more than 350,000 petroleum workers in the United States, the United Kingdom, Canada, Australia, Finland, Sweden, and Italy, we concluded that there was no increased mortality from digestive cancers (stomach, large intestine, liver, or pancreas), lung cancer, bladder cancer, kidney cancer, or brain cancer. The summary standardized mortality ratios for these cancer sites were all below unity. Significant increases of melanoma mortality were reported in some small groups of refinery workers in the United Kingdom and upstream operation workers in Canada, but no responsible agent(s) had been identified. The observed mortality from skin cancer in all other studies was similar to the expected. In particular, no significant increase of skin cancer mortality was reported in any of the U.S. studies. Elevated mortality from prostate cancer was noted in short-term workers at a U.S. refinery and in short-term workers employed in certain crafts at U.S. crude oil operations. However, the absence of an upward trend by length of employment in these workers argued against an association between exposure to petroleum products and prostate cancer. For all petroleum workers as a whole, mortality from prostate cancer was as expected.

On-Site Bioremediation Systems Reduce Crude Oil Contamination

Summary. Oilfield properties frequently have areas where soils contain concentrationsof crude oil. These soils can be either"hazardous wastes" or"designated wastes" under regulatory guidelines. As a result, propertyowners and financial institutions face potential liabilities when oilfieldproperties are transferred to new operators, abandoned, or converted to otheruses.Modern, well-designed soil bioremediation systems are cost-effective ways totreat soils that contain concentrations of crude oil, and these systems caneliminate an owner's subsequent liabilities. A modern on- sitebioremediation system requires significantly less surface area, results inlower operating costs, and provides more effective, expeditious results thantraditional land-farming practices. It also eliminates potential long-termliabilities and is typically more cost-effective than excavation and off-sitedisposal of oilfield soils. Case studies indicate that on-site bioremediationsystems have reduced crude oil contamination in soil to levels acceptable toregulatory agencies in less than 20 weeks (in some cases, less than 10 weeks). Total costs for on-site bioremediation range from $35 to $120/yd3oftreated soil, including excavation, depending on specific siterequirements.Introduction. During normal operation of oilfield properties, crude oil or other materialsfrequently leak or spill onto land surfaces. These degraded soils are commonlyassociated with oil wells, sumps and pits, tank batteries, gathering lines, andpump stations. Crude oil and drilling muds may also be found in these areasand, like the contaminated soil, they may be considered either hazardous wastesor designated wastes under current regulatory guidelines. The regulationspertaining to crude oil vary across the U.S. In California, for example, crudeoil is considered a designated waste and its off-site disposal is subject toregulations. If certain constituents (e.g., benzene) are present insufficiently high concentrations, the soil degraded by crude oil may beconsidered a hazardous wasteand subject to additional regulations. Crude oilsludge in an old sump typically contains oilfield treatment chemicals;therefore, the sludge is considered a hazardous waste.

On-Site Bioremediation Systems Reduce Crude Oil Contamination

Summary Oilfield properties frequently have areas where soils contain concentrationsof crude oil. These soils can be either"hazardous wastes" or"designated wastes" under regulatory guidelines. As a result, propertyowners and financial institutions face potential liabilities when oilfieldproperties are transferred to new operators, abandoned, or converted to otheruses. Modern, well-designed soil bioremediation systems are cost-effective ways totreat soils that contain concentrations of crude oil, and these systems caneliminate an owner's subsequent liabilities. A modern on- sitebioremediation system requires significantly less surface area, results inlower operating costs, and provides more effective, expeditious results thantraditional land-farming practices. It also eliminates potential long-termliabilities and is typically more cost-effective than excavation and off-sitedisposal of oilfield soils. Case studies indicate that on-site bioremediationsystems have reduced crude oil contamination in soil to levels acceptable toregulatory agencies in less than 20 weeks (in some cases, less than 10 weeks). Total costs for on-site bioremediation range from $35 to $120/yd3oftreated soil, including excavation, depending on specific siterequirements. Introduction During normal operation of oilfield properties, crude oil or other materialsfrequently leak or spill onto land surfaces. These degraded soils are commonlyassociated with oil wells, sumps and pits, tank batteries, gathering lines, andpump stations. Crude oil and drilling muds may also be found in these areasand, like the contaminated soil, they may be considered either hazardous wastesor designated wastes under current regulatory guidelines. The regulationspertaining to crude oil vary across the U.S. In California, for example, crudeoil is considered a designated waste and its off-site disposal is subject toregulations. If certain constituents (e.g., benzene) are present insufficiently high concentrations, the soil degraded by crude oil may beconsidered a hazardous wasteand subject to additional regulations. Crude oilsludge in an old sump typically contains oilfield treatment chemicals;therefore, the sludge is considered a hazardous waste.

Effect of environmental parameters on the biodegradation of oil sludge.

A laboratory study was conducted with the aim of evaluating and optimizing the environmental parameters of "landfarming", i.e., the disposal by biodegradation in soil of oily sludges generated in the refining of crude oil and related operations. Oil sludge biodegradation was monitored by CO2 evolution and by periodic analysis of residual hydrocarbons. The parameters studied were soil moisture, pH, mineral nutrients, micronutrients, organic supplements, treatment rate, teratment frequency, and incubation temperature. Oil sludge biodegradation was optimal at a soil water-holding capacity of 30 to 90%, a pH of 7.5 to 7.8, C:N and C:P ratios of 60:1 and 800:1, respectively, and a temperature of 20 degrees C or above. Addition of micronutrients and organic supplements was not beneficial; sewage sludge interfered with hydrocarbon biodegradation. Breakdown of the saturated hydrocarbon (alkane and cycloalkane) fraction was the highest at low application rates, but higher application rates favored the biodegradation of the aromatic and asphaltic fractions. An application rate of 5% (wt/wt) oil sludge hydrocarbon to the soil (100,000 liters/hectare) achieved a good compromise between high biodegradation rates and efficient land use and resulted in the best overall biodegradation rate of all hydrocarbon classes. Frequent small applications resulted in higher biodegradation than single large applications. Two 100,000-liter/hectare (255 barrels per acre) or four 50,000-liter/hectare oil sludge hydrocarbon applications per growing season seem appropriate for most temperate zone disposal sites.

The Operation and Regulation of Crude Oil and Gasoline Pipe Lines

Introduction, 177. — The importance of oil pipe lines, 178. — Concentration of control, 180. — Use of pipe lines by independent shippers, 182. — Minimum tender requirements, 184. — Storage facilities, 185. — Effects of shipping requirements, 186. — Rates and transportation costs, 189. — Effect of the rate and cost structure, 192. — Earnings, 193. — Subsidizing losses elsewhere, 199. — Regulation by the Interstate Commerce Commission: the Hepburn Act, 201; handicaps under which the Commission has operated, 204; Brundred Brothers vs. Prairie Pipe Line, 205; the Reduced Pipe Line Rates and Gathering Charges Investigation, 206.