A reliable, cost-effective wellhead design creates
value when constructing and equipping slimhole, monobore gas wells.
HENRY J. QUINONES, Eneva S.A., and ANTONIO PASSOS, Web Nordeste Ltda. Brazil
Driven by the identification of new business ventures
to supply energy for the northernmost areas of Brazil, and the success of the reservoir-to-wire
(R2W) production and power generation model in the Parnaiba basin since October
2019, Eneva S.A. is expanding its onshore drilling operations. The company also
holds a concession of several exploratory blocks in the Amazon basin and
operates Azulão field, which started commercial production in September 2021.
The operational success of Azulão field was greatly
influenced by leveraging the technical and economic advantages of slim monobore
wells, a technique pioneered by Eneva in the Parnaiba basin during late 2016.
Using monobore wells, Eneva implemented a significant step-change to monetize
gas production, attaining levels of operational performance and efficiency not
previously seen in the Brazilian onshore landscape.
During the 2021-2022 well campaign in the Amazon
basin, one of the key technologies deployed by Eneva was a semi-compact
wellhead system. The authors will describe the key design features of the
equipment and results of the first installations for land well operations in
Opportunity identification. Following a period with difficult and
budget-constrained market conditions, the outlook for the onshore Brazilian oil
and gas market is poised to capitalize on new growth opportunities, an
appealing shift for both operating and service companies. And to remain
competitive, it will be critical for companies to pursue new performance benchmarks
and efficiencies by leveraging innovative technologies and cost optimization
Foreseeing the potential increase of well construction
activities in the Amazon basin, a service company (Web Nordeste, or Web NE)
worked closely with Eneva to introduce a new 5k-rated wellhead system for a
3-hole section monobore well. It’s not the fully compact wellhead system that
has been broadly used by the industry to date. The updated version is slimmer
and more cost-effective. Known as the RTO3 (Portuguese acronym for “operational
time reduction”), the wellhead was to be field-tested initially in four wells
to measure the cost efficiency gains against a conventional spooled wellhead
system that was also in use during the campaign.
In addition, the collaboration between both companies
was to serve to transfer knowledge, so that Eneva’s wellsite personnel could learn
operational complexities and safely execute the installation of the RTO3 with
minimum technical support.
Design and development of the RTO3 technology. The monobore well architecture used by the Eneva
consists of three hole sections, Fig. 1. Given the constraints of the
surface location (imposed by the remoteness and unique landscape of the area), the
wells are drilled directionally, ending with a soft “S” profile in the 6 1/8-in.
production hole section, which is naturally
promoted by known formational tendencies throughout the area. Figure 2
shows the RTO3 wellhead stack-up components for monobore wells, which are: 1) the
landing base plate; 2) the 11-in. main wellhead housing; and 3) the 7 1/16-in. tubing
Top hole activities. Once the 12¼-in. hole section is completed, the 20-in.
conductor extension and flowline are removed, and the conductor pipe is cut approximately
5-in above the cellar base. Then, a two-segment landing base plate is pre-set, Fig.
3. However, it remains in an unlocked position while running the 9 5/8-in.surface
casing to avoid unnecessary interference with the upper 12-in. opening when
passing through with the casing centralizers.
To execute a safer operation, prior preparation is
necessary. The 11-in. main
wellhead housing, featuring a lower buttress threaded (BTC) box connection, is
made up to the uppermost 9 5/8-in. joint of the “as installed” running tally.
Similarly, the wellhead housing running tool (RT) is made up to the 9 5/8-in.
landing joint. Afterwards, the RT is made up to the wellhead housing, and both
connections are torqued together. There is no interference with the landing
joint to RT connection, itself, because the latter features a left-hand ACME
connection secured by a torque ring (which is removed after tightening up the
landing joint). Lastly, both joints are broken down at the left-hand RT
connection and laid down back to the pipe rack.
With the casing string close to bottom, the landing
joint is connected back to the wellhead housing, the rig crew locks the landing
base plate in place against the conductor, and the casing string is landed, Fig.
4 (left). Both a 2-in. LP bull plug and a gate valve are connected to the
side ports, and fluids returns from the cementing job are taken directly to the
cellar. The upper plate has a couple of 2-in. orifices to permit passage of
macaroni pipe, should it become necessary to perform a top job.
In addition, the RTO3 has an emergency mechanism, in
case the surface casing fails to reach bottom, Fig. 4 (right). For this
contingency, after cementing the casing and wait on cement (WOC) time, a 9 5/8-in.
slip lock adapter is made up to the wellhead housing lower BTC connection,
landed against the base plate, pressure-tested and secured accordingly.
A separate 11-in. top flange quick connector is used
to connect to the rig’s BOP stack, Fig. 5. This component is connected
to the BOP off the critical path and has a lower connection with lockdown
screws to secure it against the RTO3 wellhead housing. And, since the BOP is also
function- and pressure-tested off the critical path, the wear bushing can be
set immediately and locked in position before nippling up the BOP/quick
Intermediate hole activities. Once drilling of the 8½-in. hole section is completed,
some prior preparation of wellhead components is necessary. First, the mandrel-type
casing hanger, with a lower BTC box connection, is made up to the uppermost 7-in.
joint of the “as installed” running tally. Similarly, the casing hanger running
tool (CHRT) is made up to the 7-in. landing joint. A
torque tool is placed above the casing hanger, and the RT landing joint is made
up to it, and both connections are torqued to specifications. There is no
interference with the landing joint to the RT connection, itself, because the
latter features a left-hand ACME connection, secured by the torque tool, which
is removed after making up the landing joint.
Lastly, both joints are broken down at the left-hand
RT connection and laid down back to the pipe rack. With the casing string close
to bottom, the landing joint is connected back to the casing hanger and landed
in the main wellhead housing, Fig. 6 (left). Enough rat hole is planned to permit a safe
landing of the 7-in. casing.
Once the CHRT is retrieved, the next step is to set
the 11-in. casing hanger pack off, Fig. 6 (center). Similar procedures
to those applied for compact wellhead equipment are used, including washing the
pack-off setting area and setting the pack-off, using its dedicated running
tool on a stand of 5-in. heavy-walled drill pipe. As a contingency, should the
7-in. casing fail to reach the intended setting depth, after cementing and WOC,
the RTO3 offers the alternative to set the casing, using a slip-type casing
hanger, Fig. 6 (right). The next step is to install the tubing
head spool (THS), which features a 7 1/16-in. 5k top flanged connection. The
THS lands inside the 11-in. main wellhead housing and is secured in place by
tightening retention nuts, Fig. 7 (left).
Production hole activities. One wellhead-related design aspect of Eneva’s monobore
wells is the need to install the 7 1/16-in. THS prior to drilling the 6 1/8-in.
production hole section. As such, Web NE had to also manufacture both a
suitable wear bushing and a running/retrieving tool. Once the open hole logging
program is completed, the next step is to case with 3½-in. production tubing
and cement it in place, Fig. 7 (right). Other than accounting for the
installation of a surface-controlled subsurface safety valve, wellhead-related
activities, up to the installation of the x-mas tree, are conventional.
Implementation and results. When compared to a conventional spooled wellhead, the
key time reductions brought by the RTO3 semi-compact wellhead system are mainly
associated with the elimination of the wait-on-cement (WOC) time after 7-in.
casing operations, manual activities at cellar level (i.e., setting the casing
on slips, cut/bevel the stub–thus, reducing personnel exposure and promoting a
safer operation), and the agility with BOP activities, using the quick adapter.
Figure 8 depicts the time per well for wellhead and BOP-related activities.
Starting from Well 2, four consecutive installations of the RTO3 were
completed, resulting in an average time reduction of approximately 9 hrs, when
compared to the conventional spooled wellhead used in Well 1, which was
available from the existing stock of materials. The time reduction was sufficient
to offset the initial higher cost of the RTO3 (27%).
For future installations, the team will implement some
additional measures for better equipment readiness. For example, during
equipment preparation, Web NE will deliver all RTO3 wellhead housings and
mandrel-type casing hangers fully made up to their respective casing joints, as
well as to provide two sets of running tools for each component, already made
up to a custom-length landing joint. These measures will cut an
additional four to five hours of rig time per well. In addition, we want to highlight a few of the
additional configurations that have been pre-designed from the base RTO3
system, Fig 9.
This will allow Web NE to have the necessary flexibility to deploy it for a
variety of different onshore applications.
Opportunities and path forward. Eneva has embraced the technical and logistical
challenges of the Amazon basin by bringing fit-for-purpose technologies and
operational efficiencies. Relevant well construction-related optimizations will
remain the keystone to further promote the growth and value of its R2W model
across the northernmost areas of Brazil.
From the outset, development of the semi-compact RTO3
wellhead system was a collaborative effort between the operator and Web NE,
ultimately resulting in cost reductions that justify its deployment as the
default wellhead system for monobore wells. As such, a new contractual
agreement was signed to expand the scope of supply throughout the 2023 wells campaign.
This success case has certainly caught the eye of
other players in the local onshore industry. As a result, the Web NE RTO3 concept
started evolving into a fully configurable system to cater to other well
architectures and applications, thus paving the way for its widespread
HENRY J. QUINONES is well engineering and operations manager at Eneva S.A., responsible
for overseeing the safe and efficient planning and execution of wells campaigns
in some of the most prolific land basins in northern Brazil. He has accumulated
over 17 years of international oilfield experience, with a variety of
technical, managerial and business development-related positions for a broad
range of applications, which include high volume, land, unconventional and
offshore well construction activities. Mr. Quinones is based in Rio de Janeiro,
ANTONIO PASSOS is sales manager and consultant for WEB NE LTDA, responsible for
overseeing the Brazilian petroleum market. He is focused on developing and
presenting cost reduction solutions throughout the well construction operation
for partner players and in the application of equipment in FPSO projects top side.
With 32 years in the oilfield sector, Mr. Passos has accumulated local and
international experience in multiple petroleum business areas. His is currently
sharing his base between Rio de Janeiro and Bahia, Brazil.