This pawwas selected fw presentation by an lADC/SPE Prcgram Committee following revfew of inf~ticil mn!ained in an abs&a~submitted by he auth~r(s). c~t~nt~~the paper, as presented, have not been reviewed by the Intemationsi Asscclation of Drilting Contractors .or tbe -y of Pet$oleum Engineers and are subject to ccfrecti~by the authotis), The matertal, as presented, does not nece~rily reflect any~sition of the IADC or SPE, (heir officers, w members. Papem~esen!ed at the fADC/SPE meetings are subject b publication review by Editorial Cmmittees of the hoc and SpE. Electronic reprodu~~n, distribution, or stwage of any par-t of this paper fci commercial purpoaas without the written Cunsent of the Society of Petroleum Engmeera is prtiibited, Permission fn reproduce In print is resbicted Lo an abstract of not more than 300 wds; illustrations may not be copied. The abstract MUst contain conspicuous acknowledgment of where and by wh~the paper was presented, Write f-ibrartan, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A,, fax 01 -972-952-s435. AbstractSlips and tongs produce permanent marks on pipe body and tool joints. Such marks develop high stress concentration that reduces strength of pipes. The remaining strength of pipes often falls below the pipe stresses which can lead to tubular failure. Slim pipes are most susceptables to failure due to diemarks. In many instances, slim pipes are handled using double elevator system to reduce pipe failure. In this paper, results of a recent study of various die-mark related failures of drill pipes under different loading conditions, with particular emphasis on fatigue damage are presented. Stress concentration due to die-marks is characterised by finite element analyses as a finction of mark sizes to cover various gripping systems available in the market. Then a methodology is presented for the prediction of failure due to cumulative fatigue damage. Effect of stress concentration arising from die-marks is taken into account in the analysis. Results of this study suggest that the effect of stress concentration on the cumulative fatigue damage may be significant depending on particular gripping system in use. In most cases, the fatigue life evaluation based on conventional assumption of smooth pipe surface is found to be very unsafe. Thus, a new approach is proposed in this paper for prediction of true safe life of marked drillpipes against fatigue failure. Fatigue damage results are presented in graphical forms. Calculation of cumulative fatigue damage of drillpipes used in a number of drilling events is then presented systematically in tabular form to assist drilling engineers in the evaluation of actual remaining fatigue life of drillpipes for the target drilling event using a particular gripping system.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractUncontrolled growth of hydraulic fractures and initiation of secondary multiple fractures may occur due to execution of a fracture treatment with inappropriate values for various treatment parameters: fracturing fluid viscosity, injection rate, injection time and proppant concentration. Such uncontrolled fracturing is not only uneconomic due to increased treatment cost but may also damage the formation irreversibly, resulting in productivity lower than even unfractured wells. Also excessive pressure drawdown during production from hydraulically fractured wells may result in sand production due to mechanical failure of perforation tunnels. This paper presents an integrated model to optimize treatment parameters in order to achieve maximum possible Net Present Value (NPV) while the above mentioned formation damage aspects are avoided by satisfying various constraints. These constraints are formulated as functions of treatment parameters, fracture geometry and mechanical and petrophysical properties of the reservoir so that the critical conditions that induce the formation damage in different modes do not become active. Additional constraints are also formulated to ensure that the optimally designed treatment can be executed in the field by using the specified surface equipment, and fracture width restriction does not occur. A genetic-evolutionary computing algorithm is integrated to solve the constrained treatment design problem such that it finds optimum values for treatment parameters and fracture geometry that are formation compatible. The capability of the model is demonstrated in the paper by application to a gas reservoir.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAn excessive high treatment pressure may be required to execute a production enhancing hydraulic fracture treatment in a tight-gas reservoir, particularly if the treatment is designed with inappropriate values for treatment parameters: fracturing fluid viscosity, injection rate, injection time and proppant concentration. Such a high treatment pressure may not only exceed the delivering capacity of specified surface equipment (pump, pressure rating devices and downhole tubing), but may also cause multiple fracture initiation. Multiple fracture initiation may cause near-wellbore tortuosity complexities and large fluid loss, and thus may damage the formation irreversibly that results in productivity lower than even unfractured wells. This paper presents an integrated model for multivariate fracture treatment optimization with adequate trade-offs between production enhancement, equipment capacity and formation compatibility requirements. The model considers both fracture geometry (length, height, width etc.) as well as treatment parameters as free design variables. Compatibility relationships between reservoir properties, treatment parameters and fracture growth are formulated using a modified pseudo-3D fracture model. Design constraints are formulated to ensure that the final optimum design is compatible with specified equipment and formation characteristic to avoid the above-mentioned fracture complexities. The optimal design of fracturing treatments to maximize cumulative production is demonstrated in the paper by a series of applications of the model to a tight-gas reservoir. Sensitivity results of various parameters are also presented in the paper.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn relatively high-permeability reservoirs, the pseudo-steady state (PSS) flow condition dominates the production life of a well, and therefore modeling of production profile considering this flow condition only is found adequate. In tight-gas reservoirs, however, the early production period is dominated by the transient flow condition whereas the later period by the PSS condition. Neither of these conditions alone can be used to adequately model the production profile during the entire production life of a tight-gas reservoir. The creation of hydraulic fracture also influences the flow conditions and thus the production profile. This paper presents an analytical method, which combines both the flow conditions and account for the effect of hydraulic fracture and non-Darcy components for computationally efficient estimation of production from tight-gas reservoirs. An algorithm is then presented to couple these two different models by a production rate matching technique, which has resulted in a hybridized transientpseudo-steady-state (TPSS) model to predict the production profile during the whole production life. The production profiles and resulting pressure profiles for both TPSS and PSS models are verified by a reservoir simulator for a range of reservoir permeability. The TPSS model is found to be closer to the results from simulation for low-permeability reservoirs.
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