Key Technologies Rejuvenating Arab Oil King

A founding member of the Organization of Petroleum Exporting Countries (OPEC), Saudi Arabia continues to dominate over other oil-producing countries, contributing approximately 10% of world oil production. 

Figure1: Map of Ghawar field at the Arab-D reservoir level [1]

A huge contribution to the kingdom’s output of oil is from Ghawar field. The massive Ghawar structure is so productive that it contributes more than half of Saudi oil production and is responsible for 6% of global oil yield. In peak times, it has produced 6.5 million barrels per day. This elephant (Fig. 1) occupies an area 250 km long and 26 km and is divided into five units (Ain Dar, Shedgum, Uthmaniyah, Hawiyah, and Haradh). The nation claims that the field has 50 billion barrels left to extract. Current production stands at 5 million barrels of oil and 2 Bcf gas a day, and this level is expected to continue for several years [2].

Since the field’s discovery in the early 20^th century, world-class and cutting-edge technology has been applied to the field. Integration of multilateral wells, extended reach drilling, geosteering, gas injection, water injection, smart well monitoring and control systems, and maximum reservoir contact (MRC) wells has revolutionized the recovery from this old king. Ghawar has reportedly 3000 wells as of December 2012 [2].

This article addresses the question: How the technology has added value to the rejuvenation of this Arab oil king?

 

Geosteering

Geosteering is a process specific to horizontal drilling. It enables real-time identification of reservoir layers, allowing directional drillers to adjust the well trajectory to maximize reservoir structural characteristics and, in effect, keep wellbores within the most productive region. Logging-while-drilling (LWD), measurement-while-drilling (MWD), and mud logging acquire geological information that is continuously monitored and integrated with engineering understanding and applied to ongoing drilling. With the availability of real-time data, the operator can save time on decision making and implementing changes, thus saving rig time.

The carbonate reservoir of Ghawar field has extreme ranges of porosity and permeability, both laterally and vertically [4]. Towards the flanks, the heterogeneity index becomes severe, and prediction of lateral continuity presents challenges to planning the trajectory of the lateral wells. Hence, an utmost need was to develop a workflow that can assist in making real-time decisions about the direction the well must penetrate to get the maximum production.

Resistivity images provide an important component of reservoir characterization and contribute to real-time geosteering decisions. The technology being used in Ghawar enables differentiation of borehole and reservoir features down to 0.4 in. [5]. This technology facilitates the objective of cutting perpendicular to the maximum number of fractures to obtain increased productivity from the improved connectivity of the formation to the wellbore. 

Multilateral Wells and Smart Systems

Multiple wellbores that extend from the main hole maximize the reservoir contact, provide more drainage area, and potentially reduce drilling risk and total cost. In fact, these are also called maximum reservoir contact (MRC) wells. These wells are drilled for reduced drawdown, increased productivity or injectivity, and improved recovery factors. (Fig. 2)

 

Figure 2: Basic multilateral configurations. From left to right: Dual opposed laterals, vertically stacked laterals, and fork or fanned laterals [3]

Multilateral configurations have evolved since the 1950s and currently are divided into three main categories (Fig. 2): 

1. Horizontal fanned
2. Vertical stacked
3. Dual-opposed

The laterals are completed as
Open hole

1. Cemented liners
2. Sand Screens
3. Smart devices

Multilateral drilling in Ghawar started in 2006; initially, 32 MRC wells were drilled in the Haradh area (Fig. 1). Each lateral has approximately 4,000 ft of reservoir contact, and average contact for each well is over 14,000 ft [6]. (Fig. 3)

Twenty-eight producers were completed with “smart systems.” These systems include permanent downhole pressure and temperature sensors, production packers, and hydraulically operated downhole valves that can be controlled from surface. The downhole valves are placed in the motherbore to control flow from each lateral.

Installation of smart systems enabled the operator to better manage the water injection sweep efficiency and maximize the project output (Fig. 3).

Figure 3: Schematic map of HRDH-III initial development plan that uses MRC wells [7].

ICD Completions

The purpose of inflow-control device (ICD) technology is to effectively balance the production or injection along the lateral throughout its operational life. Otherwise, in openhole condition, a historically practiced way of completing the well in carbonates, pressure drawdown in the heel region is more than in toe, and so is the production influx (Fig. 4).

The working principle of a nozzle-type ICD is based on following equation (Bernoulli’s equation):

 

So, with an increase in fluid density (oil to water), the pressure drop increases across the ICDs, which actually retards flow from that section. Similarly, higher velocities or rates (from higher-permeability streaks) cause extra pressure drop, which retards flow from that section. The principle that nozzle-based ICDs work on is independent of the viscosity of the fluid.

The main objective of applying ICD technology in the Ghawar carbonate wells is to limit inflow from high- or super-permeability streaks and limit production from each compartment based on offset from the water-oil contact to prevent premature water breakthrough.

Figure 4: In a typical lateral well, the ICD (blue curve) reduces higher flow rate from the heel region (circled region in orange). To supplement the decreased production, the inflow rate from the lower two-thirds of the well (circled in green) is enhanced [8].

In 2006, the first test well equipped with ICD technology was recompleted in Ghawar [9]. The design was based on production logging results (Fig. 5). As a result of the ICD, the completion design suggested there would be a 50% reduction in water cut for the same liquid withdrawal in the water breakthrough case.

 Figure 5: ICD completion with five packers and six compartments [8]

CO₂ Enhanced Oil Recovery

Saudi Arabia plans to demonstrate a CO₂ capture, injection, and storage recovery project, and work has been ongoing with the King Abdullah Petroleum Studies and Research Centre (KAPSARC) [10].

This CO₂-EOR demonstration project [11] will compress and dehydrate CO₂ from the Hawiyah natural gas liquids (NGL) recovery plant, then transport the CO₂ stream 70 km to the injection site (a small flooded area in the Uthmaniyah production unit). The injection strategy is planned to consist of

1. Injection of approximately 2,000 t of CO₂ per day
2. Four injection wells, four producer wells, and two observation wells
3. Alternating water and gas (WAG) cycle of 3 months CO₂ / 3 months water
4. Well spacing of approximately 2,000 ft
5. CO₂ switching between wells

The objectives of the demonstration project are described as

1. Determination of incremental oil recovery (beyond waterflooding)
2. Estimation of sequestered CO₂
3. Addressing of primary risks and uncertainties, including migration of CO₂ within the reservoir, and
4. Identifying operational concerns

The project duration is expected to be 4 to 5 years. The design is based on extensive reservoir simulation studies and includes a comprehensive monitoring and surveillance plan.

Ghawar’s Way Ahead

Though Saudi Arabia has over 300 recognized oil reservoirs [12], most production comes from five fields, and the largest of these is Ghawar. “Is Ghawar dying?” has been an ongoing debate for the past few years. Justin Williams [13] presented a great discussion on this topic and the attempts to maintain consistent production from this field. Despite the debate, the fact remains that the field has maintained production for last few years, and its role as game changer in the foreseeable future cannot be denied.

References

[1] Sorkhabi, R. 2010. Ghawar, Saudi Arabia: The King of Giant Fields. Geo ExPro 7 (3): 24-29.

[2] Duey, R. 2015. Ghawar: the Arabian Granddaddy. E&P 88 (1): 112-113.

[3] Fraija, J., Ohmer, H., Pulik, T. et al., 2002. New Aspects of Multilateral Well Construction. Oilfield Review 14 (3): 52-69.

[4] Ehrenberg, S., Nadeau, P., and Aqrawi, A. 2007. Comparison of Khuff and Arab Reservoir Potential throughout the Middle East. AAPG Bulletin 91 (3): 275-286.

[5] Al-Musharfi, N., Bansal, R., Ahmed, M., et al. 2010. Real Time Reservoir Characterization and Geosteering Using High-Resolution LWD Resistivity Imaging. SPE Annual Technical Conference and Exhibition, Florence, Italy. 19 – 22 September. SPE-133431-MS. http://dx.doi.org/10.2118/133431-MS.

[6] AlBani, F., Baim, A.S., and Jacob, S. 2007. Drilling and Completing Intelligent Multilateral MRC Wells in Haradh Inc-3. SPE/IADC Drilling Conference, Amsterdam, The Netherlands, 20-22 February. SPE-105715-MS. http://dx.doi.org/10.2118/105715-MS.

[7] Saleri, N.G., Al-Kaabi, A.O., and Muallem, A.S. 2006. Haradh III: A Milestone for Smart Fields. JPT 58 (11): 28 – 33.

[8] Ellis, T., Erkal, A., Goh, G. et al., 2009. Inflow Control Devices – Raising Profiles. Oilfield Review 21 (4): 30 – 37.

[9] Sunbul. A.H., Lauritzen, J.E., Hembling D.E. et al., 2008. Case Histories of Improved Horizontal Well Cleanup and Sweep Efficiency with Nozzle Based Inflow Control Devices (ICD) in Sandstone and Carbonate Reservoirs. SPE Saudi Arabia Technical Symposium, Al-Khobar, Saudi Arabia. 10 – 12 May. SPE-120795-MS. http://dx.doi.org/10.2118/120795-MS.

[10] Heidug, W. 2012. Joint IEA‐OPEC workshop on CO₂‐enhanced oil recovery with CCS, Kuwait City. IEA. 7 – 8 February. http://www.iea.org/publications/freepublications/publication/HEIDUG_Workshop_Report_IEA_OPEC_FINAL.PDF (accessed 7 January 2015).

[11] Global CCS Institute. 2014. Uthmaniyah CO₂ EOR Demonstration Project. http://www.globalccsinstitute.com/project/uthmaniyah-co2-eor-demonstration-project-0 (accessed on 7 January 2015).

[12] Burgess, L. 2006. The World’s Largest Oil Field is Dying: Has Ghawar Peaked?. 9 August 2006. http://www.energyandcapital.com/articles/ghawar-oil-saudi/253 (accessed on 1 February 2015)

[13] Williams, J. 2013. Ghawar Oil Field: Saudi Arabia’s Oil Future. 19 February 2013. http://www.energyandcapital.com/articles/ghawar-oil-field/3101 (accessed on 10 January 2015).

 Note:  The article was published in Petrozene in May 2016.