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Analiza testa porasta tlaka za horizontalnu bušotinu temelji se na poznavanju protjecanja fluida u ležištu, koje je matematički opisano jednadžbom difuzije trodimenzionalnog protoka i njenim rješenjima. Prema modelu horizontalne bušotine u neograničenom ležištu za slučaj neustaljenog protoka mogu se pojaviti četiri režima protjecanja: rani radijalni protok, rani linearni, kasni pseudoradijalni i kasni linearni protok. Za svaki od navedenih protoka postoje odgovarajuća rješenja jednadžbe difuzije, koja se primjenjuju u analizi testa porasta tlaka, uz glavnu pretpostavku da je bušotina potpuno horizontalna i smještena u potpuno horizontalnom, homogenom ležištu, jednake debljine. Osim toga, ležište se uzima kao izotropno u horizontalnoj ravnini, ali da postoji vertikalna anizotropija, tj. da je vertikalna propusnost različita od horizontalne. Primjer analize testa porasta tlaka u računalnom programu Saphir prikazan je za horizontalnu bušotinu na plinskom ležištu Okoli. U analizi su korišteni podaci ispitivanja kao temelj za postavljanje odgovarajućeg modela bušotine. Primjena mjerenih podataka u modeliranju bušotine značajna je zbog točnosti i pouzdanosti, koju takvi modeli mogu dati u određivanju ključnih podataka za prognoziranje budućih promjena proizvodnog sustava, kao što su propusnost, skin faktor, početni ležišni tlak i sl., Build up test analysis for the horizontal well is based upon the theory of fluid flow in the reservoir, which is mathematically described by the diffusivity equation of the three dimensional flow and its solutions. According to the horizontal well model in the infinite reservoir for the case of the unsteady flow, four regimes can be developed: early radial flow, early linear, late pseudo-radial and late linear flow. Solutions of the diffusivity equation, that are used in the build up test analysis, are developed for each of the flow regime, supposing that the well is totally horizontal and placed in the totally homogeneous reservoir with equal formation thickness. In addition, it is considered that the reservoir is isotropic in the horizontal plane, but with the vertical anisotropy, meaning that the vertical permeability differs from the horizontal. Example of the build up test analysis in the computer program Saphir is shown for the horizontal well at the gas field Okoli. Well test data are used in the analysis as the basis for the corresponding well model design. Test data application in the well modelling is significant due to the accuracy that those models can obtain in the determination of the key parameters of the production system forecasting, such as permeability, skin factor, initial reservoir pressure etc.

Here is given the review of the book „Petroleum Production Engineering“ written by Marin Čikeš, Ph. D., a retired Full Professor of the Faculty of Mining, Geology and Petroleum Engineering of the University of Zagreb. The book was published in the year 2015, as a university textbook (Manualia universitatis studiorum Zagrabiensis).

Analiza proizvodnog sustava napravljena je za bušotinu Šandrovac-136, opremljenu neprekidnim plinskim liftom. U analizi su korišteni podaci ispitivanja kao temelj za postavljanje proizvodnog modela bušotine u računalnom programu ‘PROSPER’ (Verzija 10.3, Licenca 2681). Primjena mjerenih podataka u modeliranju bušotine značajna je zbog točnosti i pouzdanosti, koju takvi modeli mogu dati u prognoziranju budućih promjena u proizvodnom sustavu. Postavljanje modela može se podijeliti u šest koraka, od kojih su najvažniji: proračun indikatorske ili IPR krivulje, proračun sustava plinskog lifta, te ‘mečiranje’ VLP i IPR krivulja na osnovu ispitivanja bušotina. Cilj ‘mečiranja’ je odabrati odgovarajuću metodu za proračun gradijenata pada tlaka primjenom metode nelinearne regresije, što rezultira radnom točkom sustava koja u odnosu na mjerene podatke protoka i tlaka ima najmanja odstupanja. Tako postavljen model temelj je pouzdane analize osjetljivosti bušotine, u kojoj se odabirom triju ključnih varijabli prognozira njihov utjecaj na buduće promjene sustava, prvenstveno promjena protoka i dinamičkog tlaka na dnu., A production system analysis was made for the well Šandrovac-136 equipped with a continuous gas lift. The analysis was based on the test data which served as the foundation for creating a production well model in computer program ‘PROSPER’ (Version 10.3, License 2681). The importance of the measured data in well modeling is accuracy and reliability in predicting future developments of the production system. The model design can be divided in six steps among which the most important are: calculation of the IPR curve, calculation of the gas lift system and matching of VLP and IPR curves based on the well testing. The aim of the VLP/IPR matching is to choose an appropriate method for calculating the pressure drop gradient by applying the nonlinear regression method, which results in the system working point adjusted to the measured data. This model was applied in sensitivity analysis of the well, in which three key variables are selected to predict their effect on future system changes, primarily on changes of the production and bottom dynamic pressure.