Pressure-Transient Analysis of Bottomhole Pressure and Rate Measurements by Use of System-Identification Techniques

SPE Journal ◽  
2015 ◽  
Vol 20 (05) ◽  
pp. 1005-1027 ◽  
Author(s):  
M.. Mansoori ◽  
P. M. Van den Hof ◽  
J.-D.. -D. Jansen ◽  
D.. Rashtchian
Keyword(s):  
System Identification ◽  
Frequency Domain ◽  
Flow Rate ◽  
Transient Analysis ◽  
Closed Loop ◽  
Reservoir Model ◽  
Data Set ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Piecewise Constant

Summary This study presents a novel perspective on pressure-transient analysis (PTA) of downhole-pressure and flow-rate data by use of system-identification (SI) techniques as widely used in advanced process engineering. Key features of the paper are that it considers the classic PTA process from a system-theoretical perspective; derives the causal structure of the flow dynamics; proposes a method to deal with continuously varying pressure and flow-rate signals contaminated with correlated noise, which estimates physical reservoir parameters through a systematic matching procedure in the frequency domain; and can cope with arbitrary (i.e., not necessarily piecewise constant) flow-rate signals. To this end, the wellbore and the reservoir are modeled as two distinct two-port power-transmitting systems that are bilaterally coupled at their common boundary. This structure reveals that, from an SI perspective, the wellbore dynamics affect the bottomhole data as a feedback mechanism. Because of this feedback structure, it is necessary to use closed-loop SI techniques, and, because of the presence of sensor noise, the reservoir model cannot be identified solely from the bottomhole measurements. Therefore, an auxiliary signal is needed, for which we choose the surface flow rate, although other signals, such as the bottomhole temperature, could potentially also be used. Then a suitable closed-loop SI technique is the so-called two-stage method. The first stage of the algorithm removes the dynamic effects of the wellbore from the noisy data, and the second stage identifies the reservoir model in terms of rational polynomials. Thereafter, the usual physical reservoir parameters (e.g., averaged permeability and skin factor) are obtained through matching the results of the identified reservoir model and those of typical analytical reservoir models in the frequency domain, as an alternative to classic graphical or numerical type-curve analysis. The method does not rely on a piecewise constant approximation of the flow-rate signal, unlike other known PTA methods such as time-domain deconvolution. Six numerical experiments, by use of a synthetic data set, and one field example, by use of data from a real gas well, illustrate the key aspects of the proposed method.

Delivering Pressure Transient Analysis During Drawdown on ESP Wells: Case Studies and Lessons Learned

2021 ◽  
Author(s):  
Lawrence Camilleri ◽  
Mohammed Al-Jorani ◽  
Mohammed Kamal Aal Najar ◽  
Joseph Ayoub
Keyword(s):  
Real Time ◽  
Case Studies ◽  
Flow Rate ◽  
High Frequency ◽  
Transient Analysis ◽  
Continuous Production ◽  
Complete Analysis ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Production History

Abstract While pressure transient analysis (PTA) is a proven interpretation technique, it is mostly used on buildups because drawdowns are difficult to interpret. However, the deferred production associated with buildups discourages regular application of PTA to determine skin and identify boundary conditions. Several case studies are presented covering a range of well configurations to illustrate how downhole transient liquid rate measurements with electrical submersible pump (ESP) gauges enable PTA during drawdown and therefore real-time optimization. The calculation of high-frequency transient flow rates using ESP gauge real-time data is based on the principle that the power absorbed by the pump is equal to that generated by the motor. This technique is independent of fluid specific gravity and therefore is self-calibrating with changes in water cut and phase segregation. Analytical equations ensure that the physics is always respected, thereby providing the necessary repeatability. The combination of downhole transient high-frequency flow rate and permanent pressure gauge data enables PTA using commonly available analytical techniques and software, especially because superposition time is calculated accurately. The availability of continuous production history brings significant value for PTA. It makes it possible to perform history matching and to deploy semilog analysis using an accurate set of superposition time functions. However, the application of log-log analysis techniques is usually more challenging because of imperfections in input data such as noise, oversimplified production history, time-synchronization issues, or wellbore effects. These limitations are solved by utilizing high-frequency downhole data from ESP. This is possible first as superposition time is effectively an integral function, which dampens any noise in the flow rate signal. Another important finding is that wellbore effects in subhydrostatic wells are less impactful in drawdowns than in buildups where compressibility and redistribution can mask reservoir response. Key reservoir properties, in particular mobility, can nearly always be estimated, leading to better skin factor determination even without downhole shut-in. Finally, with the constraint of production deferment eliminated, drawdowns can be monitored for extended durations to identify boundaries and to perform time-lapse interpretation more efficiently. Confirming a constant pressure boundary or a change in skin enables more effective and proactive production management. In all cases considered, a complete analysis was possible, including buildup and drawdown data comparison. With the development of downhole flow rate calculation technology, it is now possible to provide full inflow characterization in a matter of days following an ESP workover, without any additional hardware or staff mobilization to the wellsite and no deferred production. More importantly, the technique provides the necessary information to diagnose the cause of underproduction, identify stimulation candidates, and manage drawdown.

A Practical Implementation of Pressure Transient Analysis in Leak Localization in Pipelines

2004 ◽  
Author(s):  
H. A. Warda ◽  
I. G. Adam ◽  
A. B. Rashad
Keyword(s):  
Numerical Model ◽  
Flow Rate ◽  
Transient Analysis ◽  
Leak Detection ◽  
Valve Closure ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Pressure Transients ◽  
Pipeline Flow ◽  
Detection And Localization

In the present study, a more realistic approach for using pressure transient analysis in leak detection and localization is proposed. In a previous publication [1] by the authors, the feasibility of using pressure transients, generated by full closure of a downstream solenoid control ball valve, in leak detection and localization is investigated. The main shortcoming of using the full closure of a downstream valve is the very high pressure rise that may reach 14 times the operating pressure. Also, full valve closure yields to discontinue the whole pipeline flow. In the present paper, a controlled partial downstream or upstream valve closure is used as a mean of generating pressure transients to overcome the above drawbacks. The percentage of the valve closure is controlled to reduce the pipeline flow rate by 20–80%. Pressure transients generated by a partial valve closure are investigated experimentally and numerically. The experimental setup consists of a 60 m long and 25.4 mm internal diameter PVC pipelines connecting two tanks. Leaks are simulated at different locations along the pipeline to investigate the effect of leak positions. The pressure time history is recorded using piezoelectric pressure transducers located at five equidistance points along the pipeline connected to a Data Acquisition System. Experiments are carried out for different leak quantities ranging from 2% to 20% of the pipe flow rate. The numerical model accounts for complex pipe characteristics, such as unsteady friction and viscoelastic behavior of pipe walls. The leak is treated as a flow through an orifice of prescribed size. The numerical model is experimentally verified to insure the capability of the model in accounting for unsteady and viscoelastic complex phenomena and efficiently simulating pressure transients in the presence of a leak.

Closed Looped Production Rate Evaluation by Means of Virtual Metering and Pressure Transient Analysis

2021 ◽  
Author(s):  
Fabrizio Ursini ◽  
Simone Andrea Frau ◽  
Francesco D'Addato ◽  
Luigi Romice ◽  
Sergio Furlani ◽  
...  
Keyword(s):  
Real Time ◽  
Transient Analysis ◽  
Closed Loop ◽  
Production Optimization ◽  
Production Performance ◽  
Production Rates ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Well Production ◽  
Well Models

Abstract The Integration of real-time high frequency data in well models allows to infer useful information regarding well and field performance. Virtual Metering (VM) algorithms aim at providing real time well rates solving an inverse problem based on flow equation in the wellbore. Although VM methodologies are based on Pressure/Temperature measurements, they rely on availability of calibration measurements. Pressure Transient Analysis (PTA) can provide useful insight for VM calibration. An innovative closed-loop workflow combining VM and PTA has been developed to face unreliable or absent rate measurements. VM requires periodical separator tests for model calibration. PTA played an important role in estimating well production rates, using it as a virtual well test to compensate the lack of field tests. VM rates are used as first guess for the PTA interpretation of build-up where production rates are unreliable. PTA log-log derivative plot is compared with the reference one which was interpreted to calibrate the formation K•H. The loop is iterated correcting VM calibration parameters until the match is acceptable. An implementation of the closed loop rate estimation workflow on an offshore oil asset is presented as an application of the methodology. The asset comprises 15 production wells, most of them with high Gas-Oil Ratio. Virtual Metering has been applied on wells fully equipped with wellhead and bottom-hole sensors. The joint application of PTA with an iterative closed loop philosophy was fundamental to compensate the lack of separator tests and of the sometimes unreliable choke opening data. The accuracy of the production profiles simulated by the VM is confirmed by the comparison with the reference asset fiscal production and by the final pressure history matching obtained with the PTA. The application of the iterative closed-loop workflow plays a fundamental role in the improvement of backallocation, in real time production monitoring and in the implementation of production optimization. Well models based on VM algorithm have been included in production optimization workflow to improve the well line-up and identify production optimization opportunities. Virtual Metering allowed to monitor results of optimization actions by estimating the actual wells production increment. This paper contains a novel approach, consisting in a reliable and robust closed loop virtual metering workflow, which integrates different tools with the common objective of assessing the actual well production rates for maximising the asset performance. The real-time data and model sharing allowed to set-up a collaborative environment optimizing effective problem solving and field production performance.

Sign in / Sign up

Export Citation Format

Share Document