M. Cook

Chapter 6 Reservoir Description

Publisher Summary The success of oil and gas field development is largely determined by the reservoirs size, complexity, productivity, and the type and quantity of fluids it contains. It is observed that in order to optimize a development plan, the characteristics of the reservoir must be well defined. However, the level of information available is often significantly less than that required for an accurate description of the reservoir and the estimates of the real situation needs to be made. It is generally difficult for surface engineers to understand the origin of uncertainty, with which the subsurface engineer must work. This chapter explores what controls the uncertainties, and how the data is gathered and interpreted in order to form a model of the subsurface reservoir. The chapter essentially discusses the common reservoir types from a geological viewpoint, the fluids contained within the reservoir, the principal methods of data gathering, and the ways in which the data is interpreted.

Chapter 1 The Field Life Cycle

Publisher Summary This chapter provides an overview of the activities carried out at various stages of field development. It is noted that each activity is driven by a business need related to that particular phase. The chapter specifically illustrates the gaining access phase, exploration phase, appraisal phase, development planning, production phase, and decommissioning. The first step an oil company undertakes in hydrocarbon exploration and production is to decide what regions of the world are of interest. This involves evaluating the technical, political, economic, social, and environmental aspects of regions under consideration. Exploration remains a high-risk activity. It is observed that the development of new exploration techniques has greatly improved geologists understanding and has increased the efficiency of exploration. Exploration and appraisal wells are now sited more accurately, and with greater chance of success. The purpose of appraisal phase is to reduce the uncertainties, in particular those related to the producible volumes contained within the structure being explored.

Chapter 9 Reservoir Dynamic Behaviour

Publisher Summary The reservoir and well behavior under dynamic conditions are regarded as the key parameters in determining what fraction of the hydrocarbons initially in place (HCIIP) can be produced to surface over the lifetime of the field, at what rates they can be produced, and which unwanted fluids are produced. This behavior can, therefore, dictate the revenue stream that development can generate through sales of the hydrocarbons. The reservoir and well performance are generally linked to the surface development plan and cannot be considered in isolation. The prediction of the reservoir and well behavior are crucial components of field development planning, and plays a major role in reservoir management during production. This chapter illustrates the behavior of the reservoir fluids in bulk of the reservoir away from the wells, in order to describe what controls the displacement of fluids toward the wells. The understanding of this behavior is extremely significant when estimating the recovery factor (RF) for hydrocarbons and during the production forecast for both hydrocarbons and water.

Chapter 7 Volumetric Estimation

Publisher Summary Volumetric estimation is largely concerned with quantifying how much oil and gas exists in an accumulation. However, the estimate can vary throughout the field lifetime due to more information becoming available, and the improvement in the technology used for gathering and interpreting the data. A volumetric estimate is, therefore, regarded as a current estimate and should be expected to change over time. The two main methods for estimating volumetrics includes: the deterministic and the probabilistic method. Deterministic methods generally average the data gathered at various points in the reservoir from well logs, cores, and seismic to estimate the field-wide properties. On the other hand, probabilistic methods use predictive tools, statistics, analogue field data, and input regarding the geological model to predict trends in the reservoir properties away from the sample points. This chapter focuses on the deterministic methods and the techniques used for expressing uncertainty in these volumetric estimates. The volumetrics of a field along with the anticipated recovery factors (RFs) often controls the reserves in the field— that is, those hydrocarbons that can be produced in the future. A reliable estimate of the reserves of a company is, therefore, important to the current value as well as the long term prospects of an oil or gas company.

Chapter 2 Petroleum Agreements and Bidding

Publisher Summary This chapter introduces the form of invitation to bid and the agreement, under which the oil companies can compete for and explore the exploration land. In offering an exploration opportunity in a block, the motivation of the government largely is to encourage investment in the form of exploration activities, such as shooting seismic and exploration drilling. It is noted that the prime objective of the oil company is to discover commercial hydrocarbons, from which it can create profits by subsequent development. The chapter describes the two broad types of petroleum agreement— namely, the license agreements and the contract agreements. In a license agreement, the government issues exclusive rights to an oil company to explore within a specific area. However, in a contract agreement, the oil company obtains the rights to an area through a contract with the government or its representative; national oil company (NOC). Essentially, the company acts as a contractor to the government, funding all the operations. The most common form of this type of agreement is a production sharing contract (PSC).

Chapter 17 Managing Decline

Publisher Summary The production decline period for a field is generally defined as starting once the field production rate falls from its plateau rate. Individual well rates can, however, drop long before field output falls. This chapter introduces some options that are available, initially to arrest production decline and consequently to manage decline in the most cost-effective manner. The field can essentially enter into an economic decline when income is falling, cost is rising, or both are happening. There can also be scope for further investment in a field in economic decline. A mature development must continue to generate a positive net cashflow and compete with other projects for funds. The chapter illustrates the options that provide some idea of the alternatives that can be available to manage the inevitable process of economic decline and to extend reservoir and facility life. The chapter specifically describes infill drilling, workover activity, enhanced oil recovery, production de-bottlenecking, and incremental development.

Chapter 15 Risk Analysis

Publisher Summary The oil and gas business involves major investments in all stages of the field life cycle. During the gaining access, exploration, and appraisal stages the expenditure does not guarantee a return and at the development stage, major investments are made in the anticipation of returns over a long period of time. It is observed that payback periods are typically long and the project is subject to large fluctuations in key variables, such as oil and gas price, and the cost of services during the producing life of the asset. Therefore, it is significant that careful technical and commercial risk analysis is performed when making decisions on investment in the industry. Moreover, the nature of oil and gas production is intrinsically dangerous, and the potential impact on the people involved is carefully analyzed and reduced to acceptable levels by the design of plant and the operating procedures. This chapter summarizes the risk analysis techniques in the areas of exploration, appraisal, and health, safety, and environment (HSE). It also describes some methods used in managing risk in development projects.

Chapter 8 Field Appraisal

Publisher Summary The objective of performing appraisal activities on discovered accumulations is to reduce uncertainty in the description of the hydrocarbon reservoir and to provide information that can help in making decision on the next action. The next action can be to undertake more appraisals, to commence development, and to stop activities or sell the discovery. In any situation, the appraisal activity should essentially lead to a decision that yields greater value than the outcome of a decision made in the absence of information from the appraisal. It is also observed that the improvement in the value of the action, given the appraisal information, should be greater than the cost of the appraisal activities, otherwise the appraisal effort is not worthwhile. This chapter describes the role of appraisal in the field life cycle (FLC), the main sources of uncertainty in the description of the reservoir, and the appraisal techniques used to reduce this uncertainty.

Chapter 5 Safety and the Environment

Publisher Summary Safety and environment are regarded as important elements of all parts of the field life cycle (FLC), and involves all the technical and support functions in an oil company. Companies largely recognize that good safety and environmental management make economic sense, and are essential to guarantee long-term presence in the market. Stakeholders, be they governments, non-government organizations (NGOs), or financing entities, can effectively scrutinize the health, safety, and environment (HSE) performance of an operator on a continuous basis. This chapter explores how HSE concerns can have a significant impact on all aspects of field development and subsequent production operations, and that safety and environment must be the concern of all employees. The chapter specifically describes the safety culture, the safety management systems, and the environment and its standards. The chapter concludes with the description of current environmental concerns, such as greenhouse emissions, gas venting and flaring, CO 2 sequestration, oil-in-water emissions, ozone-depleting substances, and waste management.

Chapter 11 Surface Facilities

Publisher Summary Oil and gas are rarely produced from a reservoir already at an export quality. The process engineer is faced with a mixture of oil, gas, and water, as well as small volumes of undesirable substances that have to be separated and treated for export or disposal. This chapter describes the processes applied to fluids produced at the wellhead in preparation for transportation or storage. Oil and gas processing facilities are generally designed to cope with produced volumes that change quite considerably over the field lifetime. The consequences of a badly designed process can be reduced throughput or expensive plant modifications after the production start-up. Essentially, most projects can be divided into four main parts— namely, wells, gathering system, processing plant, and export facilities. Though projects are often characterized by platform type, the design of a project usually starts by consideration of the process required to handle the reservoir fluids. The selection of a platform type is influenced mainly by the physical environment, in which the process plant has to be located.