Site Visit to Underground Gas Storage (UGS) at Yela (Guadalajara)   
Date: 6 June 2022

Field trip leader:
Rosa M Nieto Prieto (Enagás Transporte SAU)

Description:

Yela Underground Gas Storage (UGS from now) is located in the municipality of Brihuega, Guadalajara province, 100 km far from Madrid. Enagás, the Spanish main TSO (Transmission System Operator), operates the facilities. It is a deep aquifer converted into UGS in 2012 after more than 10 years of exploration and investigation in the center of Spain.It is an anticline with two tops. The reservoir is a dolomite formation from Upper Cretaceous at 2.300 depth and the seal is compound of anhydrites from the upper Cretaceous. It has a working gas capacity of 1bcm.



Figure 1. Location Map of Field Trip area.


The aim of the field trip is to visit the UGS facilities that include the gas treatment plant and the injection/withdrawal wells (deviated with horizontal legs) and the geological concept outcropping:

Yela Plant visit (Stop 3) (in the afternoon)

Overview outcropping geologic features of the Yela Underground Gas Storage (Stops 1&2)

For the overview outcropping of the Yela underground gas storage, the field trip aims to review the geological concept features: 

  • Reservoir rock: dolomites of the upper Cretaceous: “Santa Bárbara Dolomites”
  • Seal: anhydrites of the upper Cretaceous “Upper Evaporitic Unit”  
  • Hermetic Trap: East-thrusting anticline alpine.

Also in the field trip should be recognise other alternative reservoir (“Ciudad Encantada Fm”), initially discarded due to uncertain seal (“Margas de Alarcón Fm”)  

In the Field Trip could be seen structural sections and seismic profiles 2D and 3D examples acquires for  Enagás,  stratigraphic successions drilled in the Enagás´s Wells, and structural and stratigraphic maps for the geological model discussion.

Stop 1: The field trip will have a stop at Entrepeñas dam closure, where it can be observed the regional structural model of asymmetric anticline of the “Ciudad Encantada dolomites” (Turonian age) as analogous Yela Structure. In this point we should show the Yela-Santa Bárbara Thrusting in seismic profiles 2D (ENAGAS 2000) and 3D (ENAGAS 2001 y 2003), and in structural maps. The analogous structural sections show the principal and secondary thrusting seismic images and de normal faults associated, in time slices.The stress history of Yela Structure could be interpreted in three tectonic phases:-Alpine Compressive phase NO-SE (Upper Cretaceous-Paleocene).-Distensive phase NO-SE (Lower Eocene).-Compressive strike & slip phase NE-SO direction (Figure 2).

Figure 2. Upper Cretaceous outcrop. Located at Valdepeñas dam.



Figure 3. Close up of Santa Barbara Formation unit outcrop.



In this stop we will recognise the stratigraphic outcropping of the Fm “Margas de Alarcón” (“Ciudad Encantada” Seal) and the “Pantano de la Tranquera Fm” Dolomites in facies change (upper Turonian- lower Coniacien).In addition, in upper part, we should see the Turonian-Campanian sequence what included the Santa Bárbara Fm (Yela´s Reservoir) Finally, in this stop we could make the synthesis and discussion of the stop.





Figure 4. Upper Cretaceous Units Stratigraphic Distribution.






Figure 5. Stratigraphic Column.

Figure 6. Close up view of Santa Bárbara Limestone and its vugy porosity.

Figure 7. Geological section of Santa Bárbara Structure.





Figure 8. Interpreted Seismic Profile of Santa Barbara Structure.




Stop 2: Near Sacedon-Buendía, we would see the Campanian serie, analogous of the Yela anhydric seal (Fm Evaporítica Superior) as Yela´s reservoir seal Fm. (near to 400 m thickness in wells and partially dissolved in surface).
In this point we should show again the Yela-Santa Bárbara structure in seismic profiles 2D & 3D (Enagás 2000 ty 2003), and in structural maps.  Finally, in this stop we could make the synthesis and discussion of the stop.



Figure 9. Evaporitic Unit outcrop. Near of Buendía Village.


Stop 3: Enagas’s Yela Facility: After the safety introduction, a reservoir engineer will explain the main mechanisms of the reservoir, the injection and withdrawal cycles throughout the year, the monitoring performed and the well architecture.
Finally, the storage manage will explain the process done in the surface facilities to receive/send the gas from/to the gas network and all the group will done the site visit.


Field Trip Schedule

8:30Depart from IFEMA
10:00Arrival Outcrops - Visit different points.
14:00Lunch - Brihuega
15:30Departure to Yela underground natural gas.
15:45 Visit the facilities and explanation of reservoir behaviour and wells design.
17:30Departure to Madrid - End Field Trip

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