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Dynamic Flow Analysis The Theory and Practice of Pressure Transient and Production Analysis & The Use of data from Permanent Downhole Gauges Olivier Houzé - Didier Viturat - Ole S. Fjaere © KAPPA 1988-2008 v4.10.01 - October 2008 Olivier Houzé (OH) Engineering Degree from Ecole Polytechnique (France, 1982) and MSc in Petroleum Engineering from Stanford University (USA, 1983). After four years as a Field Engineer with Flopetrol Schlumberger, co-founded KAPPA in 1987 and has been its Managing Director since 1991. Author of several papers on Pressure Transient Analysis and co-author of the next SPE monograph on Pressure Transient Testing. Didier Viturat (DV) Engineering Degree from Ecole Centrale de Lyon (France, 1975) and from the IFP school (France, 1976). Thirteen years as a Field Engineer, Reservoir engineer and Instructor with Flopetrol and Schlumberger Testing. Eight years as Reservoir Engineer with Geoservices and Geopetrol. Head of technical support, principal trainer and consultant in KAPPA Engineering since 1999. Author of several papers on Well Test Analysis methods. Ole S. Fjaere (OSF) BSc in Petroleum Engineering from Rogaland Regional College (Norway, 1975). Ten years with Flopetrol Schlumberger as a well test and wireline operator, well test interpretation engineer and line management. Joined KAPPA in 1989 as an instructor and consultant in Pressure Transient Analysis. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p1/354 1 – Introduction OH – OSF – DV 1.A What is the purpose of this book? With this book we have tried to meet three objectives in one: • It is a stand-alone technical book that registered users can download from our WEB site. • It constitutes the reference course notes for the KAPPA training courses on Pressure Transient Analysis, Production Analysis and Dynamic Flow Analysis. It is delivered in complement to the printed hardcopies of our slides. • It also constitutes the technical reference manual of Ecrin, the integrated suite of KAPPA Software including Permanent Gauge Reservoir Surveillance module (Diamant), the Pressure Transient Analysis module (Saphir) and the Production Analysis module (Topaze). The version you are currently reading was synchronized with the release of Ecrin v4.02, and it is delivered as a complement to the on-line help and guided sessions. The book is provided as a set of PDF documents. It is not aimed at teaching software functionality. We focus here on the different methods involved in Dynamic Flow Analysis. However we shamelessly refer to our software and exclusively use KAPPA screen dumps. Actually we should put the things in the right order: KAPPA has developed its technical software coherent with what we believe to be the best methodology as of today (2006), and it is this methodology that is described in this book. This generic set of documents was initially designed as a complete and coherent book to cover the methodology of Dynamic Flow Analysis. It is not designed to follow the structure of the KAPPA software options, and will not be systematically updated with the look-and-feel of the latest KAPPA software version. Its content covers our whole range of dynamic flow courses (Foundation PTA, Advanced PTA, PA/PDG and DFA); therefore it cannot follow the path of any specific course. The challenge of this book was similar to the challenge of Ecrin: Write something that covers a wide range of disciplines, whilst avoiding duplication and confusion for those who only interested in one subject. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p2/354 A boring note on Copyrights Sorry to talk about this dull detail but this is a sign of the times. This book is the intellectual and commercial property of KAPPA. It is available on our WEB site at no cost to registrants. You are welcome to download it and print it for your own use. If you are in the academic world, or even if you are a professional instructor, you are welcome to have it printed for your students. You are also permitted to take any part of it and integrate it into other media on the condition that the copyright of KAPPA is added and visible. This applies to the copies of the copies, etc, etc. You are NOT allowed (and KAPPA reserves the right to take legal action and would): • To commercialize this book in whole or in part; • To use any part of this book in any media format without a clear reference and acknowledgement to KAPPA. We have seen in the past that some of our diagrams and figures, available from our software, on-line help or the support material we deliver with our courses, have been used in other publications. KAPPA has no objection to this however we do ask, and expect, to be acknowledged. Since the foundation of the Company KAPPA has regularly and systematically and officially registered its software and supporting diagrams and figures. In addition the figures we insert in our published documents are bitmap exports of vector (Illustrator™) original documents that we also keep and register. So we can prove both the chronological and technical history of our supporting material. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p3/354 1.B What is Dynamic Flow Analysis? By using the term Dynamic Flow Analysis (DFA), we refer to a discipline that is an extension of what used to be called Well Test Interpretation (WTI) and then Pressure Transient Analysis (PTA). ‘Dynamic Flow’ describes any intended or unintended flow process, during exploration or production operations, where diffusion of fluid takes place within a reservoir. Then, between this reservoir and one or several wells, a transient response, or responses, were recorded. This includes, but is not restricted to, all types of well test operations, formation testing, and the actual reservoir production where permanent monitoring may record rates and pressures. Fig. 1.B.1 - Dynamic Flow Analysis Dynamic Flow Analysis (DFA) is the process of handling and interpreting Dynamic Flow data in order to obtain information on the reservoir and/or the wells. DFA includes Pressure Transient Analysis (PTA) and Production Analysis (PA), also called Decline Curve analysis. When Permanent Downhole Gauges (PDG) are the source of the data, specific processing is required to permit the analysis to be performed on a PC. In addition, independent techniques such as Production Logging Interpretation (PLI) can be used to initiate multilayer interpretations and history matching. Between PLI and PTA, the processing and interpretation of permanent fiber-optic installations provide temperature and pressure versus time and depth. Temperature diffusion models can be used as an alternative or complimentary source for interpretation. The latest generation of Formation Testers also provides transient information. All these techniques are now complementary and must interact. In this initial version of the book we will focus on PTA, PA and the processing of PDG data. The need to bring PDG data processing, PTA and PA together was at the origin of the KAPPA Ecrin project. This was the industry’s first attempt to integrate all components of DFA in a single software package. The two figures below show PA and PTA performed on the same PDG data set after filtration with Diamant. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p4/354 Fig. 1.B.2 - PA in Topaze Fig. 1.B.3 - PTA in Saphir 1.C Pressure Transient Analysis (PTA) PTA has been the primary reason for the development of the tools we use today. It was initially called Well Test Interpretation. Originally this type of analysis was performed on data acquired during operations referred to as a well test. A typical well test set-up is shown in the figure below, Temporary equipment is installed downhole and at surface, the well is put on production under a predefined program and the diagnostic is performed, generally on a shut-in period after a stable production phase during which the producing rate was measured. Fig. 1.C.1 - Typical well test setup Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p5/354 To perform a Pressure Transient Analysis the rates from the tested well(s) and, where applicable, nearby wells are required. In addition the pressure response, preferably from downhole measurement, and generally acquired during pressure build-ups, are recorded. However it is always recommended to acquire the pressure response during the full production history of the test., Additional information needed includes the fluid physical properties; Pressure, Volume and Temperature (PVT) and possibly logs and geology. Fig. 1.C.2 - Analysis path The first PTA methods were introduced in the 1950’s with specialized plots (semilog, MDH, Horner) initially focused on a specific flow regime called Infinite Acting Radial Flow (IARF), where both well productivity and the main reservoir properties could be determined. Specialized plots for other flow regimes (linear, bi-linear, pseudo-steady state, etc) were also developed. Fig. 1.C.3 - MDH semilog plot Fig. 1.C.4 - Horner plot In the 1970’s loglog type-curve matching techniques were developed to complement straight line techniques. The principle was to plot the pressure response on a loglog scale on tracing paper and slide this plot over pre-printed loglog type-curves until one was selected and matched. The choice of the type-curve and the relative position of the data on this type-curve, called the match point, were then used to calculate physical results. These methods were of poor resolution until the Bourdet derivative was introduced. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p6/354 Fig. 1.C.5 - Manual Drawdown Fig. 1.C.6 - Drawdown Type Curve type curve matching In 1983, the Bourdet derivative, the slope of the semilog plot displayed on the loglog plot, considerably increased the diagnostic capability, resolution and reliability of a new generation of type-curves. Fig. 1.C.7 - Superposition plot Fig. 1.C.8 - Derivative plot Fig. 1.C.9 - Bourdet derivative type curve However, the mid 1980 saw the development of PC based dedicated software, with the possibility of directly generating models integrating superposition effects. These packages are based on modern pressure transient analysis and the use of sophisticated and user-friendly computer programs running on state-of-the-art PCs. Advanced mathematical models are used to match the measured pressure response to any disturbance, taking into account the complete pressure and flow rate history thus generating the exact model corresponding to the actual test history. Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p7/354 Models are diagnosed through pattern recognition of the different flow regimes present in a response and using the Bourdet derivative, which defines these flow regimes easily. The engineer can decide which should be the most appropriate model to apply. The methodology has a downside in that the solution(s) found are not always unique, so the engineer is challenged to search for the most consistent answer by considering all data available to him from all sources, not only the well test. Gone are the days of most straight-line analysis. MDH, Horner and other specialized analysis plots have become redundant as it is the model and the match with the real data that governs the validity of these analyses. In addition, nonlinear regression to improve results, and the development of powerful PCs, has brought the methodology to the point it is today: Fig. 1.C.10 - 1990-2000’s – PC based PTA The development of new analytical models in the 1980/1990’s and processor hungry numerical models in the 1990/2000’s converged with the availability of increasing volumes of reliable data and high speed desktop computers.. Analytical models Fig. 1.C.11 Fig. 1.C.12 Fig. 1.C.13 2K Composite reservoir Fractured horizontal well Conductive fault Dynamic Flow Analysis - v4.10.01 - © KAPPA 1988-2009 Chapter 1 – Introduction - p8/354 Numerical models Fig. 1.C.14 - Saphir analysis window Fig. 1.C.15 - 2-D Map, reservoir geometry The application of this methodology spread rapidly beyond well tests as other field operations could produce candidate data for such processing. So the name drifted from Well Test Interpretation to the more generic term Pressure Transient Analysis, although the name Well Test (WT community, WT Forum, WT monograph) remained. Pressure Transient Analysis was the correct terminology because the basic process was the interpretation of the pressure signal after correction taking into account the production history (superposition time, convolution, deconvolution, etc). Fig. 1.C.16 - Deconvolution loglog plot Fig. 1.C.17 - History match Pressure Transient Analysis was about making a diagnostic, and then using this to take decisions, including remedial action on the well and/or using the resulting model to simulate future well behavior.