Inwell measurement of rates and ratios do not allow operators to proactively control flow into the well. For intelligent fields there is a growing need for tools that enable engineers to ‘see’ further into the reservoir in order to adjust and/or change the flow control strategy as required. From a reservoir management perspective the most value can be achieved when implementing intelligent flow control systems coupled with surveillance tools. Hence, this study presents a way of defining a fit for purpose surveillance strategy that can be coupled with active flow control systems that facilitates the optimisation of the recovery efficiency. A dynamic simulator was used to analyse and determine a monitoring strategy that provides the most cost effective method of understanding various phenomena occurring within the reservoir, such as water/gas encroachment. The intention of the study was to determine if the data set currently obtained is sufficient enough to provide a deep understanding of the reservoir. The dynamic simulator modelled the temperature, saturation and pressure changes and the post-processer was used to derive corresponding changes in resistivity and acoustic properties. The change in temperature was important to model in order to study the parameter for its surveillance value as well as to capture thermal effects on reservoir fluid properties and geomechanical properties. The electro-magnetic and acoustic properties were calculated using a well-known formulae; resistivity was derived by inverting the Archie equation. Results from the study were used to specify what the surveillance tools should measure and what detection distance would allow operators to proactively adjust the flow control devices/valves in order to maximise the value of the development. Sensitivity and optimisation analysis was conducted to obtain the distance of investigation required by the surveillance. The study demonstrated that a simple 1-way coupling gives representative estimations of electro-magnetic and acoustic properties over field production time. This will be able to assist in determining which methods of surveillance can be used over the life of the field assisting in recommending a suitable data acquisition strategy to extract maximum value from the tools available; DAS/DTS/DSS/DPS/DxS, EM, seismic and other methods. Simple 1-way coupling is often enough to estimate the change with suitable accuracy to assess feasibility of various surveillance techniques. DAS could have an application in continuous cross-well tomography to follow the flood front; this subject is to be studied further.

Quantifying the vertical permeability and sealing capability of the stylolite zones in a Middle East carbonate reservoir is critically important for the enhanced recovery, water coning, perforation policy and well-placement choices. A wireline formation tester was used to perform four vertical interference tests (VIT) in a newly drilled well. The objective was to obtain permeability, permeability anisotropy and vertical communication across the stylolite zones.The formation tester was configured with a straddle packer, acting as a source of fluid flow, and two observation probes that recorded the pressure disturbances originating from the source. The formation testers were strategically placed so that the stylolite zones were located between the two observation probes. The simultaneous analysis of pressure transients from the straddle packer and the first probe provided the permeability and the permeability anisotropy of the main reservoir units. The vertical communication across the stylolite zones was evaluated by analyzing the pressure transients from the second probe.The results of the four VITs indicate varying degrees of vertical permeability across the stylolite zones, implying none have the sealing capability for fluid flow. Reservoir simulation studies were performed to evaluate the impact of stylolite sealing capacity on field performance. Results show that the model cannot match the actual production and pressure data if the stylolite zones were sealing. Therefore, this confirms that the stylolite zones in this field have no sealing capacity as shown by the VIT test results.The result of this study concludes that VITs can provide valuable dynamic data for reservoir characterization and could be extended in a field-wide approach to evaluate the lateral continuity of the vertical permeability variation across the stylolite zones. The results will be used in determining the perforation and well-placement policy and modeling the enhanced oil recovery studies.

The Underground Gas Storage (UGS) working gas capacity is one of the important design parameters for a UGS project. The objective of this paper is to demonstrate a case study from Sichuan area, China, where a fractured carbonate gas reservoir was used for UGS and show the key factors that should be considered to optimize UGS working gas capacity and help to secure energy supply during peak season. The dynamic simulation model was history matched on both depletion and storage. This model was coupled with 4D Geomechanics effects. It was then employed to capture the key parameters that will affect the working gas capacity. Based on the 4D Geomechanical integrity and facility assessment results, the forecast model was created using the subsurface and surface facility constraints. The study workflow included setting up the forecast model, uncertainty analysis and sensitivity analysis to capture the key driving parameters for the working gas volume. This study also included sensitivities of emergency gas supply during peak winter season. This study showed that the main factors that determine the UGS working gas capacity are the initial gas in place, tubing head pressure (THP) during withdrawal phase, bottom hole pressure (BHP) during injection phase, well pattern and well count. It was observed that each injection/production cycle is affected by the previous cycles. The simulation showed that the incremental working gas volume represented as a trend can be better fitted by a power function with both THP and BHP. It also demonstrated that lowering the THP limitation is more effective than increasing the BHP limitation. However, this may require surface facility upgrading. The optimum operating condition was identified by considering all engineering and geomechanical constrains such as erosion, wellbore integrity and cap rock integrity. This is used to guide the UGS daily operations with optimum production/injection rate of each well in a safe manner. The study recommended to implement a stepwise strategy to reach the working gas capacity. This paper presents a novel practical workflow and methodology to implement increased UGS reservoir working capacity. It also provides a practical way to forecast the operational pressure range and quickly predict the deliverability of emergency gas supply under various market demands.

Reservoir surveillance and integration of geological and reservoir engineering studies are essential in optimising waterflooded oil field recovery. Maintaining calibration of dynamic models can be difficult as fields mature and watercuts increase, particularly where there is significant geological complexity. This can be even more challenging if the field is multi-layered with commingled production and injection. This paper describes how the energy method (EM) and capacitance resistance method (CRM) used for inter-well communication analysis were successfully employed to provide valuable insights in two such waterflood case studies and compares their results at well and layer levels. In a preliminary step, classical waterflood surveillance and analytical techniques are combined with geological knowledge for a firm understanding of field performance. More detailed communication analysis is then performed to analyse inter-well and cross-fault communication. In a first case study, the EM technique was used to examine waterflood effectiveness in six separate panels in the most faulted area of a mature, geologically highly complex oil field. In a second case study, both the EM and CRM techniques were used to assess and optimise the waterflood in the panel of another mature oil field. The communication analyses provided a rapid route to understanding communication within complex, multi-layer fields using production data alone. In the first case study, results indicated significant communication between injectors and producers including across many of the faults separating reservoir compartments. Results identified areas of interest for infill drilling and possible workover targets. In the second case study, the combination of EM and CRM enhanced the overall understanding gained from the inter-well communication analysis.

Natural gas consumption will grow significantly in coming decades in response to cleaner energy initiatives. Underground gas storage (UGS) will be key to addressing short term supply and demand dynamics during this energy transition. This paper presents a study on the XiangGuoSi (XGS) fractured carbonate, gas reservoir onshore China which had been converted to UGS. The focus is on how integrated studies around a shared subsurface model including coupled simulation can be used to maximise working gas storage capacity and hence increase deliverability to meet future peak gas demand. Critically, the robust integration of this study raised confidence sufficiently to propose that reservoir pressure during future gas storage cycles could be increased above the original (pre-production) pressure.