This paper describes a systematic study of the effect of condensate blockage on the productivity index (PI) of hydraulically fractured wells in a complex, highly heterogeneous reservoir containing rich gas condensate. The study was performed for the Smorbukk field offshore Norway with sophisticated simulation models. The techniques used are general, and the study findings apply as guidelines in general to fractured gas-condensate wells. Proppant fracturing is capable of restoring most of the productivity lost owing to liquid buildup. The effectiveness depends primarily on the reservoir heterogeneity, fracture length and conductivity. The relative benefits of fracturing decrease in highly heterogeneous formations.
This paper describes the study of the effect of the water blockage for a well in the Bossier play in Texas. The history of the well was modeled with a coupled reservoir and fracture model, which accounts both for the dynamic fracture propagation during the job and the static fracture during production. The model was constrained by the interpreted microseismic data, 2-phase cleanup, production and buildup data, thus reducing the uncertainty in the interpretation. The results show convincingly strong geomechanical permeability effects, which can be deduced from clean-up data. Water blockage alone has a small effect on well productivity, but formation damage can have a noticeable effect. In addition, the use of PTA to identify the various features was also investigated. Introduction Waterfracs have been used increasingly in recent years as a low-cost alternative to conventional fracturing of low permeability gas wells. While commercially successful, they are not necessarily optimal from the point of view of well productivity. One of the aspects not well understood is the effect of the large amount of water pumped with no leak-off control on the productivity of the well, in particular in formations where significant capillary effects are present. Placement of the water in the formation is a function of the dynamic fracture geometry, which in turn may be influenced by geomechanical effects, in particular stress-dependent permeability. Prior to the availability of microseismic imaging, such problems were difficult to analyze because multiple solutions could exist. The imaging of the created fracture geometry makes the realistic modeling of the process possible. The "Bossier Play" is located directly between Dallas and Houston. It is an Upper Jurassic sandstone that typically lies at a depth of 12,500 ft to 15,000 ft. The first "Bossier Play" well was completed in April of 1996. The first well was marginally economic, therefore costs became the focus. Drilling efficiencies were significantly increased and completion costs were significantly decreased. With the combination of lower costs and exploration success, the "Bossier Play" has grown to its current size of approximately 450 Anadarko operated wells producing approximately 300 MMCFD gross. The Bossier is a tight sandstone that requires a fracture stimulation. Wells initially produce at a high gas rates (10 MMCFD) and decline hyperbolically. The purpose of the work was to investigate the water blockage by modeling and quantify its effect on productivity. An additional goal was to quantify if the blockage or formation damage can be identified from data signatures in PTA (buildup) testing. The geomechanical parameters were obtained by a detailed analysis of the well described in this paper. Following this, the various influences on productivity were investigated for a hypothetical well representing a typical Bossier well. History of the well The well used for detailed study in this example was spud in May 2001 and completed in the Bossier. The well was fractured with 10,000 Bbls of Slickwater and 170,000 pounds of 40/70 RCS at an average rate of 80 BPM with an average wellhead pressure of 7524 psig. In addition, the fracture was microseismically imaged using an offset wellbore. The well was produced for approximately 3 months and then shut-in for two weeks to perform a pressure build up. Reservoir characteristics Anadarko developed an extensive set of reservoir characterization data for the Bossier, including capillary pressure, relative permeability and stratigraphy data. In addition, detailed stress log and mechanical properties data was available. Stress-dependent permeability data was measured on a number of core samples.
>SDE \/01)31Sum......,. A new method of partial decoupling of the problem of modeling a hydraulic fracture in a reservoir is described. This approach has significant advantages over previous methods with either fully coupled or completely uncoupled models. Better accuracy can be achieved in modeling the fracture propagation, and the new system is very efficient and versatile. Virtually any reservoir model can be used for predicting postfracture productivity. Examples of single-and multiphase applications for modeling fractured wells are discussed.
Produced water re-injection at high rates presents a coupled problem of reservoir flow, formation damage, stress alteration around the injector, and fracture propagation. Accurate prediction of permeability changes, fracture propagation pressure, and fracture dimensions is required for minimization of disposal costs and design of surface equipment. The paper presents the formulation and numerical implementation of a coupled reservoir, damage and geomechanical model which includes the above couplings. Details of the model are first described. A simple empirical damage model, calibrated to field data is then presented. Finally, application of the complete model to high rate reinjection in the Masila Block in Yemen is presented. The model predictions show that it is feasible to sustain over 100,000 BWPD in a single Masila disposal well by injecting above fracture pressure. Introduction Oil production operations often produce large volumes of water and high rate produced water re-injection (PWRI) is usually the best method of water disposal. However, injection wells can experience large reduction of injectivity due to plugging caused by solids and oil in water1,2. In particular, the combination of total suspended solids (TSS) and oil-in-water (OIW) is particularly damaging2 and can cause equivalent skins on the order of 200 or more. Consequently, injection pressures increase with time and induced fracturing may take place. The prediction of injectivity and fracture propagation in injectors experiencing damage is a complex coupled problem including multiphase flow, geomechanics (stress changes), formation plugging, and fracture mechanics. This paper describes the formulation and numerical implementation of a model, which treats all of the above phenomena. The model is an extension of a previous coupled reservoir and geomechanics model3,4, combined with a dynamic fracture propagation feature and permeability reduction model. There are several possible approaches to fracture propagation modeling, which will be discussed in detail. The plugging mechanics is based on a simple, yet realistic model that can be easily implemented in any conventional simulator. The formulation described here has been implemented in the GEOSIM modeling system and also in the Open Eclipse environment. The software has been used to model the PWRI injection in the Masila block in Yemen, operated by Nexen Inc. Although the details of the engineering study are beyond the scope of this paper, the methodology of conducting such studies and the consequences of the plugging mechanics for history matching will be presented in detail. The model shows in particular the importance of the coupling between the plugging, which generates increased pressure gradients, the associated poroelastic and thermoelastic stress changes, and the resulting fracture propagation pressure. Formulation of the model The coupled model consists of four main components:Fluid flow modelDeformation and stress modelDynamic fracture modelPermeability damage model Because the formulation of the first two components has been described previously3,4, this Section will give only a brief overview and highlight the couplings between them, followed by a detailed discussion of the fracturing and the damage model in the following Sections. Reservoir flow. This part of the system is a conventional 3-dimensional 3-phase black oil simulator. This model is the "host" or "master" for the other components. In the actual implementation, of the software, the host reservoir model can be either Eclipse 100 or the DE&S thermal reservoir simulator TERASIM. Reservoir flow. This part of the system is a conventional 3-dimensional 3-phase black oil simulator. This model is the "host" or "master" for the other components. In the actual implementation, of the software, the host reservoir model can be either Eclipse 100 or the DE&S thermal reservoir simulator TERASIM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.