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Foothills fortune

In the face of drilling and production challenges of a level typically seen only in deep water, engineers at Total have brought the first phase of the Incahuasi gas project in Bolivia online.

The location in the Andean foothills is remote, the topography and drilling challenges are extreme, and the area is a sensitive ecosystem that is home to numerous indigenous communities.

Despite it all, Total announced last year that seven years after drilling the AQI-X1001 exploration well and more than a decade after drilling the 5600-metre deep ICS-X1 discovery well, production had begun at the massive Incahuasi gas project in Bolivia.

1702.7957 REMOTE LOCATION: Bolivia’s Cordillera foothills created significant logistics challenges to Incahuasi drill sites, located 250 kilometres from the nearest supply centre.  Photo: Total

The Incahausi gas and condensate field, 250 kilometres from the city of Santa Cruz de la Sierra, is one of largest such fields in the country.

Developed by a Total-led consortium that includes partners Gazprom, Tecpetrol and YPFB Chaco, production from the three phase one development wells had come on line in August 2016.

The consortium has estimated production for Incahuasi’s first phase to reach 6.5 million cubic metres per day of gas and nearly 6000 barrels per day of condensate.

Because of its location, no part of the development work at Incahuasi — drilling three wells through hard-to-define lithology, or connecting them through 150 kilometres of pipeline to a central processing facility (CPF) and then to a gas export line — came easy.

1702.Pierre  Photo: Total
"It may be the hardest rock in the world."
Pierre Leclerc, Total

“We were drilling in the mountains and there was no geological prediction,” says Total drilling and completion manager Pierre Leclerc. “We were drilling blind and did not know what to expect in the next metre or the next formation.”

Company engineers connected the first three wells to the CPF across difficult terrain shaped by the same geological forces that made the subsurface so difficult to navigate.

“It was very difficult to build a CPF and lay pipe in this remote area and on very steep slopes that caused technical and mainly safety challenges,” says Stephane Venes, Total’s project manager who oversaw all aspects of construction, including pipelines and the CPF.

Hard rock country

The geological forces that created the Cordillera foothills of the Bolivian Andes mountains also generated a subsurface composed of folds and thrusts formed as the earth was forced upward.

In the process, hydrocarbon-bearing formations were buried beneath mountains of very hard rock originally formed deep in the Earth’s crust, resulting in a subsurface maze of complex traps and fractures that defy seismic imaging.

“In 2009, we drilled the confirmation well in a very difficult environment,” says Leclerc. “It may be the hardest rock in the world. We had to work with service companies to find the best bits and the best parameters to increase (rate of penetration) as much as possible.”

Incahuasi Difficulties: the surrounding landscape provided logistical challenges for project leaders at Incahuasi.  Photo: Colin Dunlop
 

Drilling the top sections of the hole through very hard overlaying rock was particularly slow going. Some bits were worn within 100 metres and others had to be pulled after cutting through less than 10 metres.

Once through the hard, shallow formations, drilling was made difficult again by an unstable formation at the top of the reservoir. The exploratory well required 550 days to reach total depth. That was reduced to 480 days on the second well and to one year for the third well.

Besides being hard and abrasive, the rocks of the Cordillera foothills have complex and varying stress regimes. These stresses often impose significant torsion and friction forces on the bottom hole assembly (BHA).

“There was lots of torque-and-drag,” says Leclerc. “We had to adapt continuously to try to understand the rock and to change mud properties. The exploration well had five sidetracks because the BHA became stuck in the well.”

1702.location.jpg ON STREAM: One of Incahuasi phase one's three well sites.  Photo: Colin Dunlop
 

Sidetracks were common in these first wells, although better understanding of rock mechanics have decreased the number of sidetracks in more recent wells.

While a deviated well drilled with rotary steering systems kept the wellbore within striking distance of the reservoir, penetration rates suffered because drillers found it difficult to control trajectory in the hard rock sections.

Time considerations also played a role in the Incahuasi drilling fluids programme. Because of the extended drilling times required to drill each section, engineers chose simple mud types that did not contain additives that might degrade and affect overall mud properties over time.

Initially, Total engineers chose to drill the upper sections of the well using gel polymer water-based mud but were persuaded by heavy fluid losses to switch to a thixotropic system.

Thixotropic systems help reduce fluid losses by generating a highly viscous “skin” around the wellbore that slows fluid leak off to the formation. After the hard rock was drilled, drillers switched to an oil-based mud to counteract interaction with the shale and reservoir rock.

1702.Stephen  Photo: Total
 

"Every day we moved hundreds of people between the construction site and the city."
Stephane Venes, Total
 

To ensure company and state environmental standards were met, Total brought a thermal treatment unit to the rig site to clean and dry oily cuttings and deployed a closed loop drilling mud system.

Because it had to be imported and transported to the remote location, the choice came at a cost. “By internal rules, we do not use diesel based mud,” explains Leclerc. “We imported low toxicity, environmentally friendly EDC 95-11 Total base fluid, and that represented some logistical problems.”

Leclerc describes the producing formation rock as being more like marble than a sandy reservoir. Marked by very low permeability, production from the formation is dependent on a fracture network that is only imprecisely modelled, which leads to well placement uncertainties.

“If we are lucky, we are in a good place,” he says. “If not, we have to sidetrack to see if 100 or 200 metres over there is a good fracture network. It is very difficult to understand and model.”

1702.0699.jpg STEEP SLOPES: The 150-kilometre pipeline connecting Incahuasi to the gas processing facility crosses terrain with inclines that in places exceed 40 degrees.  Photo: Total
The existence of a fracture network also has convinced the company that acidising or hydraulic fracturing would be ill-advised at Incahuasi, fearing that stimulations may expand fractures that reach to aquifers.

On the third well, engineers drilled a horizontal section that crossed numerous natural fractures and Total is now assessing the value of that strategy.

Completions at Incahuasi are basic by design, although deploying them can be challenging. Because of expected high production rates, the design calls for seven inch production tubing, which requires a 9 5/8-inch casing shoe be set at the top of the reservoir.

Casing crews and engineers, therefore, have almost no room for error because hole enlargement is problematic in the unstable shale above the producing interval.

 

To market

Remote, difficult terrain and environmental and human concerns were important considerations in drilling and completions operations. They were pivotal to every aspect of the pipeline and CPF projects.

The three wells of the first phase are connected through pipelines to the CPF and then to the export line tie-in point through 150 kilometres of pipeline.

Sections of the pipeline traverse terrain with slopes that sometimes exceeded 40 degrees. The logistics of the project, which at its peak activity levels included up to 3000 people working at six different sites, were formidable.

“One of the biggest risks in onshore projects is transportation,” says Venes. “Every day we moved hundreds of people between the construction site and the city. During the project, we travelled overall almost 20 million kilometres.”

1702.CPF LOCAL CONTENT: Contractors hired more than 2400 local workers to build the pipeline and central processing facility, pictured.  Photo: Total
 

Much of that travel was tied to transportation of 30-inch pipe imported from India and 10-inch pipe imported from Argentina.

Because Bolivia is a landlocked nation, the 30-inch pipe arrived at the port of Arica in Chile and was transported 1500 kilometres to the construction site by truck. Safely managing the movement of that much weight required the company to implement stringent transport procedures.

“We put in mechanisms to be sure transportation was done properly,” says Venes. “We had to make sure everything was considered on the contractor side.”

Total designated mandatory truck stops in cities along the route at which the conditions of the trucks and the drivers were examined.

Truck speed was monitored by GPS and the trucks were escorted by mechanics in vehicles with spare parts. In more than 1600 truck trips, no accidents were reported.

Co-operative effort

In the end, the entire project, including the pipeline and CPF construction and start up, was completed without major incidents.

Venes attributes that outcome to a co-operative effort between contractors and Total that included adherence to internal safety policies, contractors’ compliance with those policies and Total’s recognition of the value of the contractors’ expertise.

“We have to listen to the contractor also, because he is in charge,” says Venes. Incahuasi pipeline contractor Spiecapag “is a well-known piping company that knows how to work in difficult situations. Nevertheless, we have continual meetings to make sure safety is in place.”

Managing impact

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Local support was critical for the success of the geographically widespread undertaking. Before it began any step of the project, Total made certain that those living nearby were aware of the work to be performed and assured that it would have a positive affect on the area.

Employing local workers was also a critical part of the company’s community outreach effort.

“Every time a contractor requested a work force, they employed local people as a priority,” says Venes.

“The pipeline crossed five communities and we had to negotiate with them. It was a day to day, hour to hour concern to make sure the project is well accepted.”

Despite all that could go awry on such a large and difficult project, the pipelines and the CPF were all completed under budget, Venes says.

No saving too small

The company looked to save money wherever it could without compromising on safety. Some cost-reduction measures saved considerable sums of money, including an early decision to abandon plans to build a dedicated airstrip. Others saved relatively few dollars, but nonetheless contributed to overall project savings.

“We had an internal campaign to study everything that can be saved,” explains Venes.

“Everyone could propose a saving and no saving was too small. If we can save a thousand dollars, we do it. Of course, the first rule was to not jeopardise safety but we challenged almost everything. And doing this, you can do some very good savings.”

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20 Feb 09:40 GMT
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