Integration of Thermodynamics in Ensemble Modeling for Gas Development Project

Study was conducted to evaluate development of gas-bearing formations in the Azerbaijan sector of the Caspian Sea. Study considered subsea wellheads tied into subsea manifold, and that manifold tied to offshore facility. Flow Assurance required the calculation of subsea Flowing Wellhead Temperature (FWHT) and Pressures (FWHP). 242 subsurface scenarios were conducted with reservoir model. To accommodate all subsurface scenarios in flow assurance assessments, it was required to carry out FWHT/P calculations for all. Reservoir model was equipped with vertical lift performance curves for pressure loss calculations in tubing and logic for pressure loss estimation in subsea system. If correctly calculated, [FWHP >= dP(subsea) + Pseparator] logic should have been satisfied. As the reservoir model was not set for FWHT calculations, an external tool was required to cope with that task. Both nodal analysis software and dynamic flow modeling were considered as appropriate tools. However, as nodal modelling allowed much more automation, it was decided to use nodal analysis over dynamic modelling. To improve FWHP calculations: the logic was built into the reservoir model to: ○ estimate dP(subsea) from gas rate vs pressure drop curves ○ confirm validity of [minFWHP(wells 1, 2…n) >= dP(subsea) + Pseparator] statement: step was re-iterated until the statement was satisfied To improve FWHT calculations: Enthalpy Balance method was tested for gas wells with 1-2% error against actual data Then, nodal analysis models with the same method were built for the project wells Code was developed to calculate FWHT as part of the ensemble model predictions in following steps: ○ Well properties of each prediction step were transferred to nodal analysis software. ○ kH was varied until nodal analysis software calculated gas rate matched to ensemble model output within 1mmscf/d error Summary: Described methods allowed to significantly increase accuracy in FWHT and FWHP calculations and accommodate all possible subsurface scenarios in Flow Assurance evaluation Integration of subsea and topside hydraulics in subsurface modelling is important to develop flow assured design for development Enthalpy Balance temperature prediction method provides good match to actual data Use of coding provides huge opportunities to automate data analysis Paper will present different approach to calculation of FWHT and FWHP in subsurface modelling, integration of subsea and topside hydraulics in subsurface modelling via alternatives ways, use enthalpy balance temperature modelling, integration between nodal analysis and subsurface modelling and coding can prove analysis of large subsurface data set.

Lessons Learnt from Integrated Production Modelling and Performance Analysis of Gas Lift Wells of One of the Biggest Offshore Complexes in India

The paper aims to discuss various issues pertaining to gas lift system and instabilities in low producer wells along with the necessary measures for addressing those issues. The effect of various parameters such as tubing size, gas injection rate, multi-porting and gas lift valve port diameter on the performance analysis of integrated gas lift system along with the flow stability have been discussed in the paper. Field X is one of the matured offshore fields in India which has been producing for over 40 years. It is a multi-pay, heterogeneous and complex reservoir. The field is producing through six Process Complexes and more than 90% of the wells are operating on gas lift. As most of the producing wells in the field are operating on gas lift, continuous performance analysis of gas lift to optimize production is imperative to enhance or sustain production. 121 Oil wells and 7 Gas wells are producing through 18 Wellhead platforms to complex X1 of the field X. Out of these 121 oil wells, 5 are producing on self and remaining 116 with gas lift. In this paper, performance analysis of these 116 flowing gas lift wells, carried out to identify various problems which leads to sub-optimal production such as inadequate gas injection, multi-porting, CV choking, faulty GLVs etc. has been discussed. On the basis of simulation studies and analysis of findings, requisite optimization/ intervention measures proposed to improve performance of the wells have been brought out in the paper. The recommended measures predicted the liquid gain of about 1570 barrels per day (518 barrels of oil per day) and an injection gas savings in the region of about 28 million SCFD. Further, the nodal analysis carried out indicates that the aforementioned gas injection saving of 28 million SCFD would facilitate in minimizing the back pressure in the flow line network and is likely to result in an additional production gain of 350 barrels of liquid per day (65 barrels of oil per day) which adds up to a total gain of 1920 barrels of liquid per day (583 barrels of oil per day). Additionally, system/ nodal analysis has also been carried out for optimal gas allocation in the field through Integrated Production Modelling. The analysis brings out a reduction in gas injection by 46 million SCFD with likely incremental oil gain of ~100 barrels of oil per day.

Gas Deliverability Monitoring and Reserves Quantification without Shut-In the Well: Application of Coupled Material Balance - Nodal Analysis Approach in Main Zone of Tunu Field, Mahakam

The classical Material Balance (P/Z) plot requires fully shut-in built-up reservoir pressure (Pr) for its calculation by generating static Pr as a function of cumulative gas production (Gp). Shut-in the well only for Pr data acquisition is impractical and creates several issues such as risk of production loss and production disturbance. Mattar & McNeil (1997) introduced Flowing Material Balance approach for gas deliverability monitoring and reserves estimation based on surface well flowing parameter by creating parallel line through the initial Pr to estimate Initial-Gas-In-Place (IGIP). The method is practical for qualitative purpose, but any dynamic behavior of the well will be challenging. Improved model is presented, a Coupled Material Balance - Nodal Analysis approach for gas deliverability monitoring and reserves quantification of connected gas in place volume (CGIP). Initial Pr as a known variable then extended by the decline of Pr as a function of Gp and improved by performing “flowing mode” Nodal Analysis, converting bottom hole flowing pressure from wellhead flowing pressure to determine estimated Pr. Pr uncertainty and its depletion could be identified by sensitivity analysis, such as inflow productivity and water encroachment evolution. This approach has been applied for well T-32 of Tunu field, a mature field in Mahakam, to perform as single-reservoir gas deliverability monitoring by using only flowing parameter data. The “flowing” mode of Pr estimation with actual Gp, gives good performance of CGIP estimation without any shut-in activities, since this well is one of the big gas producer. This model also handled the dynamic activities of operation: well movement, production curtailment and improvement. The unknown variable of continuous water encroachment is also handled by wellbore temperature model which justified with actual data. This improved model could be considered as an alternative approach for gas reserves quantification and gives advantage for production strategy.

A Computational Model for Wells’ Performance Analysis

The ability to identify underperforming wells and recover the remaining oil in place is a cornerstone for effective reservoir management and field development strategies. As advancement in computing programming capabilities continuous to grow, Python has become an attractive method to build complicated statistical models that predicts, diagnose or analyze well performance, efficiently and accurately. The aim of this study is to develop a computational model that will allows us to diagnose and analyze well performance using nodal analysis with the help of python. In this study, python was used to compute Nodal analysis method using Darcy and Vogel Equations. A case study was carried out using the data obtained from a field operating in the Niger Delta. Again, sensitivity of tubing size was conducted using python. The results obtained showed that a computational model with python has the ability to visualize, model and analyze wells performances. This technique will petroleum engineers to better monitor evaluate and enhance their production operation without the need for expensive softwares. This will reduce operating cost increases revenue.

EVALUATION OF ESP PERFORMANCE DN1800 TO INCREASE WELL PRODUCTIVITY

The use of the Electrical Submersible Pump (ESP) in the oil lifting method is very popular because it is easy to install, less required installation of tools in the field and a high efficiency. To achieve the Q target, ESP parameters such as the number of stages and RPM need to be analyzed to align with the IPR (Inflow Performance Flow) curve. The use of nodal analysis is used to determine the relationship between Pwf and head pump. Iteration needs to be done to determine the range of the number of stages so that it aligns with characteristics of well. It is found that the recommended range stage is 580-600 at a well depth of 7684 ft. Moreover, it is found that with 3600 RPM and 600 stages is able to reach the Q target. The relationship between the number of stages and RPM value with Pwf is inversely proportional.

Sudanese Oil Field Production Performance by Nodal Analysis Technique

The study has evaluated production performance of oil well by using nodal analysis for entire production system. The goal of this study is to analysis one of the Sudanese oil field using nodal analysis and to review the field completion strategy for the respective field. The study starts by collecting the data from oil Company and takes the X Field as case study. The X field consist of 18 well and four of them were selected for theanalysis namely X NW-1, X NW-2, X NW-3 and X NW-4. Operating pressure for each well are 2409, 2455, 2550 and 2420 psia, and operating flow rate are 3925.4, 1110.4, 2255.7, and 1387.2 STB/D respectively. Wellfl modeling used for this task, which permits the production optimization of oil well using the concept of nodal analysis. Several sensitivity analyses were conducted in order to get the production forecast. If assumed thatthe depletion in the pressure occur within 1 year, the pressure reduced to 2000 and 1000psia for each well; as can be seen, the production reduced rapidly inXNW-2 and XNW-4. However, 1000psia the production becomes zero for the four wells.

Nanoprobe Nodal Analysis with Stitch Diagram in Local Fault Isolation

In order to understand and communicate a PFA strategy during an analysis, a two-dimensional diagram of the layout of a suspect net has been developed. Net connections are extracted from the layout and drawn in a two-dimensional stitch diagram. The result is a simplified diagram providing a stack view of the layout layers for the net(s) of interest. Key analysis decisions are made and communicated using the stitch diagram. Using this diagram, selective nanoprobe measurements are made. Software implementation that extracts and draws the diagram allows for faster creation as well as making larger nets practical. As examples show, nanoprobe curve trace analysis using a simplified diagram has proven to be a successful evidence based approach to physical failure analysis of complex nets.