vbox-resize-vdi
C:\Program Files\Oracle\VirtualBox>VBoxManage.exe modifyhd "C:\Users\maquetas\VirtualBox VMs\maquesol\soldiskoraclebi.vdi" --resize 16000
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%

And now at the solaris box we create a new usable partition:

root@solasoa:/export/home/looser# format
Searching for disks...done

AVAILABLE DISK SELECTIONS:
       0. c1t0d0 <ATA-VBOX HARDDISK-1.0-16.00GB>
          /pci@0,0/pci8086,2829@d/disk@0,0
       1. c1t2d0 <ATA-VBOX HARDDISK-1.0-16.00GB>
          /pci@0,0/pci8086,2829@d/disk@2,0
       2. c1t3d0 <ATA-VBOX HARDDISK-1.0-17.58GB>
          /pci@0,0/pci8086,2829@d/disk@3,0
Specify disk (enter its number): 2
selecting c1t3d0
[disk formatted]

FORMAT MENU:
        disk       - select a disk
        type       - select (define) a disk type
        partition  - select (define) a partition table
        current    - describe the current disk
        format     - format and analyze the disk
        fdisk      - run the fdisk program
        repair     - repair a defective sector
        label      - write label to the disk
        analyze    - surface analysis
        defect     - defect list management
        backup     - search for backup labels
        verify     - read and display labels
        inquiry    - show disk ID
        volname    - set 8-character volume name
        !<cmd>     - execute <cmd>, then return
        quit
format> format
The protection information is not enabled
The disk will be formatted with protection type 0
Ready to format.  Formatting cannot be interrupted.
Continue? y
Beginning format. The current time is Thu May 24 13:01:15 2018

Formatting...
done
no reserved partition found

Verifying media...
        pass 0 - pattern = 0xc6dec6de
   36863946

        pass 1 - pattern = 0x6db6db6d
   8627850
   36863946

no reserved partition found
Total of 0 defective blocks repaired.
format> format>