Intelligent-Completion Installations in the Santos Basin Presalt Cluster
This paper presents information regarding the installation of intelligent-well completions (IWCs) in the Lula and Sapinhoá fields of the Santos basin presalt cluster (SBPSC).
This paper presents information regarding the installation of intelligent-well completions (IWCs) in the Lula and Sapinhoá fields of the Santos basin presalt cluster (SBPSC). The technology is intended to improve reservoir-management capability by using remotely operated flow-control valves and real-time pressure and temperature monitoring for each perforated interval, corresponding to different reservoir zones. The benefits are obtained at the expense of additional challenges for well engineering because well-completion design becomes more complex and overall associated risks increase.
The area known as the presalt cluster in the Santos basin is located in ultradeep waters, between 1900 and 2400 m, approximately 290 km from Rio de Janeiro in southeast Brazil. Fig. 1 (above) shows the main blocks of the presalt cluster currently in the appraisal-plan or production-development phases.
The first areas selected for production development were Tupi (BM-S-11 Block) and Guará (BM-S-9 block), which now are known as the Lula and Sapinhoá fields. Initially, extended well tests were performed in these areas to gather information and test some of the technologies that would be applied on further developments. Later, a production pilot project was initiated in Lula field by the deployment of a production system with a total of nine wells (six producers and three injectors). Since then, new production systems are being deployed continually in the Lula and Sapinhoá fields.
Since the SBPSC initial phases, IWC was considered one of the more appropriate designs for production-development projects in the field. This technology is expected not only to improve reservoir management but also to provide better capabilities to deal with reservoir uncertainties, which is imperative in carbonate reservoirs.
Internal risk-analysis assessments before the first production-development project supported the decision to use a two-zone hydraulic system to actuate the inflow-control valves (ICVs). The choice was based on the advice of specialists who considered it to be the simplest and most reliable system in the long term and recognized that it is a field-proven solution. On the other hand, wet trees designed for SBPSC projects contain a multiplex control system, which adds additional integration issues to be addressed during the planning phases.
Multiposition ICVs were selected to provide improved reservoir-management capability. Eight different positions are specified for each field, six with choke positions, which gives some control on the flow rate for production from or injection into each zone. Both valves in each well are operated with three dedicated control lines, one of which is common to both valves and is known as the common close line, with the other two being dedicated each to a specific valve. Because there is a common line, a specific operational logic must be followed while operating the ICVs, to prevent any undesired movement.
One of the key factors for the project’s success was the integration between the IWC and the wet-tree control systems. In the first SBPSC project, the logic to operate ICVs was included on the master control system (MCS) installed onboard the production unit. Therefore, the IWC provider had to inform the subsea vendor of the operational logic to be implemented in the MCS. The interface card for the permanent downhole gauge (PDG) was installed inside the wet-tree subsea control module (SCM) in order to use the same communications link to the floating production, storage, and offloading vessel. An extensive integration process was conducted to ensure that every interface would perform per plan during the production phase.
On later projects, an alternative architecture for the control systems was defined. A more-flexible solution was necessary because different service companies were expected to provide the IWC systems for subsequent wells and different subsea providers were contracted to supply subsea equipment. The new arrangement consisted of implementing the ICV operational logic outside the MCS, including additional equipment in the IWC package. This equipment is known as the intelligent-well-control system and was designed to communicate with the MCS with a standardized protocol. The intelligent-well-control system is allowed to actuate the directional control valves that apply pressure to the ICV control lines and to receive feedback from the SCM pressure sensors and flowmeter placed in the open-to-sea return line. Additionally, the PDG interface card was installed outside the SCM, in a dedicated pod in the wet tree, eliminating the need to change the SCM according to the IWC supplier.
Up to now, 25 wells have been completed with IWC for dual zones; seven are injectors, and the others are producers. A significant decrease in completion duration has been observed during this period. Most recent wells took approximately 50% of the time to complete when compared with the initial wells. The two main causes for delays during IWC deployments were misruns because of damage on control lines and tubing-hanger-seal failures.
Three of the major IWC suppliers have provided the systems installed on these wells. Some issues were observed with equipment engineering and manufacturing quality control. In one case, a failure to meet dimensional requirements partially compromised the intervention as planned, and, subsequently, an alternative solution for lower-zone isolation was necessary to maintain IWC functionality. In another case, an ICV was observed being stuck in the closed position after system deployment. Attempts to open it were unsuccessful, and, because of that, the contingency sliding sleeve was opened by use of slickline to re-establish access to that zone. Investigations indicated that this particular ICV model was operating too close to its operational limits, and some engineering failures and gaps on qualification were identified. The use of this specific ICV has been suspended until a redesign on the equipment is made and a new qualification process is performed. These events, despite being unacceptable failures, have not fully compromised the system capabilities so far. In the one case, some additional controls were necessary to keep the valve operational, while, in the other, an intervention with a rig will be necessary to operate the mechanical sliding sleeve that was left open.
Four IWC-system misruns occurred because of poor protection on control lines at IWC-assembly depth. This issue has been mitigated successfully for subsequent wells, and no damage was observed on the last 11 wells. Issues on landing the tubing hanger also led to two unsuccessful first runs on the IWC system, something that has been fixed with a new seal design for the hanger.
A considerable number of IWCs are under way or are expected to take place in the near future; therefore, learning from previous installations is a key factor for improving performance and reliability. Fifteen IWC wells are already in the operational phase, and all attempts to cycle valves have been successful. PDGs also work properly on most of these wells. Because IWCs have been deployed successfully, improved reservoir management is expected to be possible on SBPSC fields.
Despite some challenges faced on a few wells, the deployment of IWC systems has been successful on the SBPSC fields. The systems installed remain operational, and most of them are already contributing to an improved reservoir-management capability. ICV remote actuation has been used for several purposes, including controlling gas production, well testing with the production unit, sharing commingled injection or production, proactively managing water breakthrough, and testing the surface-controlled subsea valve. Additional benefits are expected to be obtained in the future as more wells become operational and the fields mature.
This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 174725, “Road to Success and Lessons Learned in Intelligent-Completion Installations at the Santos Basin Presalt Cluster,” by E. Schnitzler, D.A. Silva Filho, F.H. Marques, F.K. Delbim, K.L. Vello, L.F. Goncalez, and T.C. Fonseca, Petrobras, prepared for the 2015 SPE Annual Technical Conference and Exhibition, Houston, 28–30 September. The paper has not been peer reviewed.