This is an HTML version of an attachment to the Freedom of Information request 'Horse Hill request for information'.

Horse Hill Developments Ltd
Horse Hill-1 (LR/24-4)
Extended Well Test Application - Supplemental Information

Per  our  WONS  extended  well  testing  (EWT)  application,  Horse  Hill  Developments  Ltd  (HHDL)  is
seeking OGA’s consent for a further EWT of the Horse Hill-1 (HH-1) well. This document provides
supplemental information, namely:

-  HH-1  test  intervals,  Portland  test  programme,  Kimmeridge  Limestone(s)  test
programme and testing operations sequence.

Test Programme Objectives
The primary objective of each of three tests is to establish that a minimum commercial volume of
oil in place (OIP) is connected to each of three previously tested oil pools. To estimate connected
OIP volumes a measurable pressure drop under steady state flow conditions must be achieved.
Currently the plan aims to achieve a pressure drop of around 10-15 psi, i.e. large enough to be
unambiguous but small enough to avoid dropping below the bubble point pressure to avoid free
gas  within  the  reservoir  that  may  complicate  any  estimate  of  total  system  compressibility.  The
steady state pressure drop therefore requires a minimum volume of oil to be produced.

It should be noted that in order to obtain steady state flow conditions the well will be significantly
choked back to below the flow rate that could be achieved during future sustainable production.
The tests and outline flow rates are designed to minimise the amount of free gas in the system of
each oil pool, i.e. keep the area surrounding the well bore above bubble point pressure.

Base Case Test Sequence
The  overall  base  case  testing  programme,  consist  of  3  separate  tests  of  three  “independent”
reservoirs/oil pools, namely:

-  Test 1: Portland Sandstone conventional reservoir
-  Test 2: Kimmeridge Limestone 4 - naturally fractured reservoir
-  Test 3: Kimmeridge Limestone 3 - naturally fractured reservoir

Table 1 below shows the base case test intervals:

Table 1: HH-1 Well Test Intervals
Horse Hill-1

MD (ft)
TVD (ft)
TVDSS (ft)
Test 1 Portland

Top perf

Base perf

Test 2 KL4
Top perf

Base perf

Test 3 KL3
Top perf

Base perf

-  Can KL3 and KL4 be commingled as one zone? If so, what is a sustainable flow rate?
-  Why is there a difference in PI between KL3 and KL4 zones? Is it that KL4 was cleaned
up via acidisation, or that KL3 was damaged due to longer acid residency?

Each KL test will follow the concept and methodology, below:

Table  3  below,  illustrates  the  current  outline  testing  sequence,  flow  rates,  shut  in  periods  and
associated  durations.  It  should  be  noted  that  this  is  an  outline  plan  and  may  be  modified
dependent on the data gathered from the initial two short duration flow and shut in periods.

Table 3: Outline KL3 and KL4 Test Sequence

KL3 and KL4 zones -  *PER* ZONE TEST PLAN - PLUS Potential Additional Co-mingled Flow.
Rate - bopd
Duration - hours
Cum. Production - bbo
Get initial pressure
See above….
Cumuative hours
Cumulative Days

Downhole  gauges  may  be  left  in  place  as  part  of  the  well-suspension  programme  –  this  will  be
decided  towards  the  end  of  the  sequence  of  tests.  The  aim  of  such  monitoring
is  to  understand  gravitational  effects  to  help  refine  estimates  of  System  Compressibility  and
possible interference testing with regional KL wells e.g. Broadford Bridge-1, Brockham, Balcombe.

Contingent Programme

Dependent  on  achieving  the  primary  testing  objectives  within  the  time  allowed  under  planning
consent, one or more short duration contingent tests may be undertaken to include one or more
of the following zones:

-  Test 4: a commingled test of KL3 and KL4. If sufficient time we plan to produce from
one KL completion zone and monitor the pressure in the other completion zone
-  Test  5:  a  new  short  duration  test  of  the  previously  untested  deeper  KL2  and  or  KL1
zones, similar in duration/scope to the early Portland/KL3 and KL4 flow periods

Base Case Extended Well Test Operations Sequence:
Figure  1,  below  illustrates  the  current  status  of  HH-1,  i.e.  as  left  following  well  testing  in  2016.
Note that the test zones are as labelled in 2016. The Portland is test zone 3, KL4 test encompasses
zones 2/2a and KL3 zone 1.

Kimmeridge Limestone test operations (for each of KL3 and KL4):
















Depending on the results of the flow tests, a decision will be made on whether to run a dedicated
suspension string.

Additional works may include: