The Hassi R'Mel Field is a gas condensate reservoir with three Triassic sands
(A-B-C) separated by a thick shale layer. Producing wells were drilled in the
Northern-Central-Southern part with two lines of dry gas injection.
A decrease in the production wells was observed. Build-up tests realized on
those wells showed significant skin, which is due primarily to the excessive
invasion mud used during drilling and workovers.
A study was undertaken in order to see what method is to be used to optimize
and improve the potential of these wells, which is less than hoped for given
their petrophysic characteristics. Stimulation by acidizing was decided upon
and three companies were selected to complete the program.
During this program, 34 wells were acidized, which was carried out in three
phases in order to diversify the methods. Of the 34 wells, 13 wells were chosen
for the first phase, 13 wells for the second phase and the remaining eight
wells were in the third phase.
In order to study the stimulation's effects, PLTs were performed before and
after each acidizing phase.
The purpose of this paper is to show:
- The various methods of acidizing and the concentrations used in each of the
- Interpretations of the PLTs which enabled us to obtain flow layers, dynamic
flowing pressure, static pressure, drawdown pressure and the productivity index
in order to calculate the gain in production in each layer, the gain in
production for each well and the flowing pressure.
The combination of the PLT's results carried out on the acidized wells will
be analyzed and shown in table form and graphs, which will enable us to draw a
conclusion on the advantages and disadvantages of this stimulation
Sandstone matrix stimulation has been the subject of extensive investigations
for over 40 years and extensive experimental work has been conducted to
investigate the reactions of various mud acid systems with damaging and
formation materials(1-3). Theoretical analysis and modelling of the
stimulation process have also been studied by some
In this study, we wanted to share our experience of acidizing which was done in
the Hassi R'Mel Field with different types of acids and various acidizing
The Hassi R'Mel Field is located 500 km southward from Algiers in the Algerian
Sahara. It was discovered in 1956 and is one of the largest wet gas reservoirs
in the world.
This field has three distinct reservoir horizons: Zones A, Band C.
Zone A sandstones are composed of very fine grained sandstones which are
locally clay-rich with anhydritic cementing in some places. Zones B and C have
very good reservoir quality with gas permeabilities ranging from 300 to 1,200
mD. Zone A also has very good reservoir quality, but its permeability is lower,
at less than 300 mD.
The productivity of Zones A, B and C has been reduced over time. Build-up tests
performed on those wells had shown significant skin due to excessive invasion
of mud used during drilling and workovers.
© 2009. Petroleum Society of Canada (now Society of Petroleum Engineers)
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- Original manuscript received:
16 January 2006
- Meeting paper published:
7 June 2005
- Revised manuscript received:
5 May 2008
- Manuscript approved:
6 April 2009