West Gulf Coast Tertiary Basin

The first permanent electrical distributed temperature array system (EDTA-S) was installed with a single trip in water injection wells in the Perdido fold belt, Gulf of Mexico. The oil field is offshore in the Alaminos Canyon block ultradeepwater environment, which consists of heavily faulted sand formations. Water injection is part of field development, and the risk of out-of-zone injection (OOZI) has a negative impact on the pressure support in the oil zone and causes part of the injected water to be allocated to an undesired formation and reducing hydrocarbon recovery.

The EDTA-S was identified as a technology solution to monitor OOZI. It comprises a permanent array of high-resolution temperature sensors distributed across the formation and overlying caprock with discrete dual-sensor pressure and temperature (PT) gauge measurements. A subsea acquisition card interfaces with the subsea control module, sending power and telemetry to the system via an electric cable installed across the completion. The sensors are installed below the feedthrough packer and positioned on a shroud offset from the tubing to thermally decouple the sensors from the tubing and enable monitoring of the formations. The installation is supported with a data interpretation platform that the operator’s technical teams review to assess whether injected water has been rerouted from the reservoir to some other sink, such as a fractured caprock. This ensures that production is maximized by establishing all the injected volume in the reservoir zone.

The first operator to deploy the permanent EDTA-S subsea used it in one water injector in 2016, and one in 2017. To deploy the array system in a single-trip completion, several enabling components were developed and qualified, including an electrical feedthrough system for the tree/hanger, subsea and topside control integration, shrouded tubing for the array sensors, and a feedthrough control line set packer. The completion operations went according to plan, and the sensors were positioned to monitor 100 m of formation above the perforations. The monitoring system was successfully integrated with the subsea controls and topside system and provides real-time monitoring of the injection and warmback periods. A biweekly system data health check shows good quality of data. Warmback data analysis indicates cooling in the nonperforated sand formation and possible water invasion is moving upward. To date, there is no evidence of OOZI into the caprock or channeling to the wellbore. Advanced thermal modeling software was used for interpretation, and a good match has been obtained with sensor measurements. Modeling of warmbacks confirms the data analysis result with no evidence of OOZI currently in caprock. However, continuous monitoring provides value in that it will capture any behavior changes over time.

The paper details the integration of components, execution, and data interpretation of EDTA-S in the Perdido fold belt. There is a significant potential for implementation of this system in deepwater developments to increase recovery factors.

Mexico’s Energy Ministry had successfully implemented tender processes for exploration blocks and farm-out opportunities in the southern Gulf of Mexico (GoM). Significant discoveries have been announced by foreign companies in the shallow waters of the Campeche area, following the award of many deepwater blocks and the selection of Pemex’s partner for the development of the Trion oil discovery.

A key challenge faced by explorers in the southern GoM is to establish and validate the economic potential of the exploration opportunities using seismic amplitudes. This validation required the development and implementation of an interpretation framework for calibrating rock properties to seismic amplitudes. Empirical observations and rigorous theoretical modeling indicate that both Neogene and Paleogene exploration plays are amplitude-supported.

We built a robust and comprehensive Rock Physics (RP) model and associated interpretation framework that leverages an uniquely comprehensive local calibration data base with over 50 wells. The new predictive framework for Neogene and Paleogene exploration plays, fully integrated with petrology, pore pressure prediction, and basin modeling has been used for a confident screening and interpretation of the seismic amplitudes in terms of lithology, porosity, and fluids.

These integrated Quantitative Interpretation (QI) workflows have been effectively applied at regional and prospect scales to reduce reservoir and pore-fluid uncertainties. This regional work is an important component of Shell’s approach to block and prospect ranking, and has been part of the selection process for top leads. Additional field-scale QI work is also helping with a better understanding and evaluation of farm-out opportunities.

Presentation Date: Tuesday, October 16, 2018

Start Time: 1:50:00 PM

Location: 210C (Anaheim Convention Center)

Presentation Type: Oral

Each of the 25 onshore blocks offered to private companies in Mexico's December auction were awarded, almost all of which went to Mexican companies. It was the third installment of the country's historic Round One auction process made possible by a 2013 constitutional reform that for the first time in a generation allows private companies to extract oil and gas in Mexico. The results of the latest auction exceeded expert predictions as well as those of the Mexican government that prior to the auction, had announced it would consider five awarded blocks to be a success. Only five out of 19 blocks were awarded in the shallow water auctions held earlier in 2015. In total, 22 of the blocks were awarded to 13 Mexican companies and consortia, with three other blocks going to a Canadian oil company.

Mexico's second deepwater bid round failed to disappoint as 19 of 29 blocks were awarded, including nine to Anglo-Dutch supermajor and Mexican offshore newcomer Shell. Eleven international firms from 10 countries bidding individually and in consortia won blocks--thought to be mostly oil-rich--in the Perdido Fold Belt, Cordilleras Mexicanas basin, and Salina basin of the Gulf of Mexico. Nineteen firms from 15 countries placed 39 bids overall. The winning bids comprised 44,178 sq km, 23 well commitments, and $525 million in tiebreak payments. Mexico's National Hydrocarbons Commission (CNH) announced the results 31 January in Mexico City.

Summary

This case study presents results from the Orion project within the Gulf of Mexico’s Lloyd Ridge area. Difficulties arose in updating the velocity within the Cotton Valley Formation (CVF), a thin low-reflectivity layer of shale with carbonate stringers. The prestack depth migration (PSDM) common-image gathers (CIGs) and stack displayed noticeable undulations. To reduce the undulations, an offset-dependent residual moveout (RMO) picking technique was combined with high-resolution tomographic inversion to update the velocity model. The combined work flow resulted in a higher resolution velocity model, which enhanced the gather flatness and reduced the undulations of the event beneath the CVF layer.

Description
In 2012, Pemex announced some major oil discoveries in a new exploration region with its first two Ultra Deep Water exploration wells. The first achieved the deepest well ever drilled in Mexico to a depth of 6,119 m and the second achieved drilling in the deepest water depth at 2,900 m. These wells have confirmed that Perdido has a high potential for commercial production. This reservoir was found in Lower Tertiary geological system.
Applications
Problems incurred while drilling out from under the large casing sizes (22”, 18”, 16”) with tandem hole enlargement bottom hole assemblies. Shallow reservoirs need to be evaluated for hydrocarbon potential, but these shallow hole sections are in very large hole sizes that require optimizing the drilling and formation evaluation. The objective here is to drill, evaluate and enlarge with the same BHA. During the same trip, the simultaneous enlargement of the hole is made to avoid a second under reaming trip (22”, 20”, 17 ½”, 16 ½”, 13 ½”).
The shallow vertical depth of the reservoirs and the shallow geohazards requires a directional well design avoids the shallow hazards and the directional build section is intended to intersect the drilling target. An alternative strategy is to acquire the full suite of wireline logs in a dedicated 12 ¼” pilot hole. Subsequently, an under-reaming trip is made for the hole enlargement. This second option is also very time consuming.
Results
The drilling group has evolved a tandem drilling assembly from traditional hole enlargements of 17½”x20" or 12¼”x 14 3/4" to more complex simultaneous drilling and hole enlargements BHA’s of 12 ¼”x 16 ½”x20” or 12 ¼”x14½”x17 ½”. These new assemblies incorporate the rotary steerable system with mechanical and hydraulic hole openers, plus a complete set of LWD measurements for supporting the real time formation and geo-mechanical evaluation. This combination assures that in one run, the hole is drilled, evaluated, and enlarged, reducing well bore stability risk, and saves time and resources.
Significance of Subject Matter
Pemex evaluated the reservoirs in the discovery of commercial quantities of hydrocarbons that can possibly double the oil reserves of Mexico

Waterflooding can supply additional reservoir energy for producing substantial quantities of oil trapped due to limited displacement drive and poor sweep efficiency. However, water injection is not commonly used in the deepwater Gulf of Mexico (DW GoM) due to good primary recovery, drilling cost and facility limitations. In over 80 fields and 450 reservoirs, water injection program has been implemented in only 18 reservoirs in 13 fields, or less than 5% of potential waterflooding candidates.
DW GoM mid-Miocene reservoirs are characterized by sparse well counts, over-pressured, and generally good rock and fluid properties. Rock compaction and moderate aquifer influx often provide moderate to good natural drive energy and oil recovery. Primary oil recovery averages 32% with the 80% confidence range between 16% and 48%. However, Paleogene reservoirs are characterized by deeper depth, high pressure, high temperature, complex geology, and rock and fluid properties. Estimated recoverable oil is only 10% of OOIP assuming primary production and limited natural drive energy. Water injection programs will be difficult to execute in tight, abnormally-pressured Paleogene reservoirs. Waterflooding of deepwater turbidites has accumulated many lessons and learns now, and a comprehensive understanding of the influence of depositional environment and injection into over-pressured, highly compacting rocks is necessary. This paper is a detailed examination of Pleistocene-to-Upper Miocene age turbidite reservoirs in the DW GoM under water injection. Issues on waterflooding these deepwater plays were reviewed in the context of geological setting and depositional environment. Despite many drawbacks that tend to oppose the implementation of a waterflooding in Paleogene reservoirs, this paper still proves that they are candidates for water injection programs under the rules of good production practice. Moderate oil recovery is suggested in highly compacting reservoirs with supplemental injection drive. Overall, waterflooding strategies have proven to be highly effective in achieving good incremental oil recovery from the deepwater Gulf of Mexico reservoirs.