Well Completion

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Tulsa Community College *

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2034

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Industrial Engineering

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Oct 30, 2023

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TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 1/50 PE 4063 / 6463 – Well Completion GROUP – 1 Introduction to Well Completions SET 1 – Introduction The word "completion" means the conclusion of a borehole that has just been drilled. Completion is, therefore, the link between drilling the wellbore and the production phase. Completion involves all of the operations designed to make the well produce, in particular connecting the borehole and the pay zone, treating the pay zone, equipping the well, putting it on stream and assessing it. Pay zone is the reservoir rocks which contain oil and/or gas that can be recovered. Generally speaking, certain measurement and maintenance operations in the well along with any workover jobs that might be required also come under the heading of completion are considered. Therefore, completion begins with well positioning and ends only at well abandonment. Whatever the operational entity in charge of well completion and workover, its actions are greatly influenced by the way the well has been designed and drilled and by the production problems the reservoir might cause. The "completion man" will therefore have to work in close cooperation with the "driller" (who may both work in one and the same department), and also with reservoir engineers and production technical staff. TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 2/50 After a well has been drilled, it must be properly completed before it can be put into production. A complex technology has evolved around the techniques and equipment developed for this purpose. Consequently, the selection of materials, equipment and techniques should only be made following a thorough investigation of the factors which are specific to the reservoir, wellbore and production system under study. Thus, completion engineer should be in coordination of many different professionals. As seen from the following figure, the completion engineers should be in contact with drilling engineers, reservoir engineers, production engineers, geologists, etc. Therefore, completion process required a massive teamwork.

TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 3/50 There are three basic requirements of any completion (in common with almost every oilfield product or service). A completion system must provide a means of oil or gas production (or injection) which is; i) Safe ii) Efficient iii) Economic Current industry conditions may force operators to place undue emphasis on the economic requirement of completions. However, a non-optimized completion system may compromise long-term company objectives. For example, if the company objective is to maximize the recoverable reserves of a reservoir or field, a poor or inappropriate completion design can seriously jeopardize achievement of the objective as the reservoir becomes depleted. In short, it is the technical efficiency of the entire completion system, viewed alongside the specific company objectives, which ultimately determines the completion configuration and equipment used. Well completion processes extend far beyond the installation of wellbore tubulars and equipment. Installing and cementing the production casing or liner, as well as logging, perforating and testing are part of the completion process. In addition, complex wellhead equipment and processing or storage TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 4/50 requirements effect the production of a well so may have some bearing on the design and configuration of the completion. Well Completion Planning Planning a completion, from concept through to installation, is a complex process comprising several distinct phases. Many factors must be considered, although in most cases, a high proportion can be quickly resolved or disregarded. Ultimately, it is the predicted technical efficiency of a completion system, viewed alongside the company objectives, which will determine the configuration and components to be used. Data Sources In order to select the suitable completion type as well as conduct a proper completion design, information should be gathered from different possible sources. Following figure summarizes the sources that are used for this purpose.

TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 5/50 Reservoir Parameters The information about the reservoir can be obtained by formation and reservoir evaluation programs such as coring, testing and logging. Typically, such data will be integrated by reservoir engineers to compose a reservoir model. The reservoir structure, continuity and production drive mechanism are fundamental to the production process of any well. Frequently, assumptions are made of these factors, which later prove to be significant constraints on the performance of the completion system selected. TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 6/50 Physical characteristics of the reservoir, such as pressure and temperature, are used in describing reservoir and downhole conditions. The effects of temperature and pressure on many other factors can be significant. For example, corrosion rates, selection of seal materials and the properties of produced fluids are all affected by temperature and pressure. When investigating the reservoir rock characteristics, the principal concern is assessing formation behavior and reaction. This includes behavior and reaction to the drilling, production or stimulation treatments which may be required to fully exploit the potential of the reservoir. The formation structure and stability should be closely investigated to determine any requirement for stimulation or sand control treatment as part of the completion process. The reservoir characteristics effecting completion configuration or component selections are best summarized by reviewing the reservoir structure, continuity, drive mechanism and physical characteristics. Produced Fluid Characteristics Two conditions, relating to the chemical properties of the produced fluid most affect the physical qualities of completion components and materials. These are chemical deposition (scale, asphaltenes etc.) and chemical corrosion (weight loss and material degradation). The ability of the reservoir fluid to flow through the completion tubulars and equipment, including the wellhead and surface production facilities, must be

TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 7/50 assessed. For example, as the temperature and pressure of the fluid changes, the viscosity may rise or wax may be deposited. Both conditions may place unacceptable backpressure, therefore causes a dramatic reduction the efficiency of the completion system. While the downhole conditions contributing to these factors may occur over the lifetime of the well, consideration must be made at the time the completion components are being selected. Cost effective completion designs generally utilize the minimum acceptable components of an appropriate material. In many cases, reservoir and downhole conditions will change during the period of production. The resulting possibility of rendering the completion design or material unsuitable should be considered during the selection process. Wellbore Construction Wellbore construction factors can be categorized in the following phases; i) Drilling – The processes required to efficiently drill to and through the reservoir ii) Coring and testing – The acquisition of wellbore survey and reservoir test data used to identify completion design constraints iii) Pre completion stimulation or treatment – final preparation of the wellbore through the zone of interest for the completion installation phase. TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 8/50 It is an obvious requirement that the drilling program must be designed and completed within the scope and limits determined by the completion design criteria. Most obvious are the dimensional requirements determined by the selected completion tubulars and components. For example, if a multiple string completion is to be selected, an adequate size of production casing (and consequently hole size) must be installed. Similarly, the wellbore deviation or profile can have a significant impact. Drilling and associated operations, e.g., cementing, performed in the pay zone must be completed with extra vigilance. It is becoming increasingly accepted that the prevention of formation damage is easier, and much more cost effective, than the cure. Fluids used to drill, cement or service the pay zone should be closely scrutinized and selected to minimize the likelihood of formation damage. Similarly, the acquisition of accurate data relating to the pay zone is important. The basis of several major decisions concerning the technical feasibility and economic viability of possible completion systems will rest on the data obtained at this time. A pre-completion stimulation treatment is frequently conducted. This is often part of the evaluation process in a test treat-test program in which the response of the reservoir formation to a stimulation treatment can be assessed.

TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 9/50 Completion Assembly Installation This stages marks the beginning of what is commonly perceived as the “completion program”. Considerable preparation, evaluation and design work has been completed before the completion tubulars and components are selected. With all design data gathered and verified, the completion component selection, assembly and installation process commences. This phase carries obvious importance since the overall efficiency of the completion system depends on proper selection and installation of components. A “visionary” approach is necessary since the influence of all factors must be considered at this stage, i.e., factors resulting from previous operations or events, plus an allowance, or contingency, for factors which are likely or liable to affect the completion system performance in the future. The correct assembly and installation of components in the wellbore is as critical as the selection process by which they are chosen. This is typically a time at which many people and resources are brought together to perform the operation. In general, completion components are broadly categorized as follows i) Primary completion, components ii) Auxiliary completion components. Primary completion components are considered essential for the completion to function safely as designed. Such components include the wellhead, tubing string, safety valves TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 10/50 and packers. In special applications, e.g., artificial lift, the components necessary to enable the completion system to function as designed will normally be considered primary components. Auxiliary completion components enable a higher level of control or flexibility for the completion system. For example, the installation of nipples and flow control devices can allow improved control. Several types of device, with varying degrees of importance, can be installed to permit greater flexibility of the completion. While this is generally viewed as beneficial, a complex completion will often be more vulnerable to problems or failure, e.g., due to leakage. The desire for flexibility in a completion system stems from the changing conditions over the lifetime of a well, field or reservoir. For example, as the reservoir pressure depletes, gas injection via a side-pocket mandrel may be necessary to maintain optimized production levels. Completion fluids often require special mixing and handling procedures, since; i) the level quality control exercised on density and cleanliness is high ii) completion fluids are often formulated with dangerous brines and inhibitors.

TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 11/50 The ultimate selection of completion components and fluids should generally be made to provide a balance between flexibility and simplicity. Initiating Production The three stages associated with this phase of the completion process include; i) Kick-off ii) Clean up iii) Stimulation The process of initiating flow and establishing communication between the reservoir and the wellbore is obviously closely associated with perforating operations. If the well is to be perforated overbalanced, then the flow initiation and clean up program may be dealt with in separate procedures. However, if the well is perforated in an underbalanced condition, the flow initiation and clean up procedures must commence immediately upon perforation. While the reservoir/wellbore pressure differential may be sufficient to provide an underbalance at time of perforation, the reservoir pressure may be insufficient to cause the well to flow after the pressure has equalized. Adequate reservoir pressure must exist to displace the fluids from within the production tubing if the well is to flow unaided. Should the reservoir pressure be insufficient to achieve this, measures must be taken to lighten the fluid TU – PE 4063/6463 – Well Completion Fall 2023 Ozbayoglu M.E., 918-631 2972, evren-ozbayoglu@utulsa.edu Group-1, Set-1, 12/50 column - typically by gas lifting or circulating less dense fluid. The preparations for these eventualities are part of the completion design process. The flowrates and pressures used to exercise control during the clean up period are intended to maximize the return of drilling or completion fluids and debris. This controlled backflush of perforating debris or filtrate also enables surface production facilities to reach stable conditions gradually. In some completion designs, an initial stimulation treatment may be conducted at this stage. An acid wash or soak placed over the perforations has proved effective in some conditions. However, as underbalanced perforating becomes more popular, the need and opportunity for this type of treatment has diminished. Stimulation There are four general categories of stimulation treatment which may be considered necessary during the process of completing a well i) Wellbore cleanup ii) Perforation washing or opening iii) Matrix treatment of the near wellbore area iv) Hydraulic fracturing Wellbore clean up will not normally be required with new completions. However, in wells which are to be reperforated or in which a new pay zone is to be opened, a well bore clean up

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