Al-Kandary, Ahmad (Kuwait Oil Company) | Al-Fares, Abdulaziz (Kuwait Oil Company) | Mulyono, Rinaldi (Kuwait Oil Company) | Ammar, Nada Mohammed (Kuwait Oil Company) | Al naeimi, Reem (Baker Hughes) | Hussain, Riyasat (Kuwait Oil Company) | Perumalla, Satya (Baker Hughes)
Role of geomechanics is becoming increasingly important with maturing of conventional reservoirs due to its implications in drilling, completion and production issues. Exploration and development of unconventional reservoirs involve maximizing the reservoir contact and hydraulic fracturing both of which are heavily dependent on geomechanical architecture of the reservoirs and thus require application of geomechanical concepts from the very beginning.
To support the unconventional exploration and conventional reservoir development in Kuwait, country-wide in-situ stress mapping exercise has been carried out in nine fields of Northern Kuwait. Stringent customized quality control measures were put in place to evaluate stress orientation. Cretaceous and sub-Gotnia Salt Jurassic rocks exhibit distinct patterns of stress orientations and magnitudes. While the variations in stress orientation in the Cretaceous rocks are within a small range (N40°E-N50°E) and consistent across major fault systems, the Jurassic formations exhibit high variability (N20°E-N90°E) with anomalous patterns across faults as well as in the vicinity of fracture corridors. Moreover, the overall stress magnitudes were found to be much higher in the strong Jurassic section compared with the relatively less strong Cretaceous strata. During the analysis, it was also observed that several natural fractures in Jurassic reservoirs appear to be critically stressed with evidences of rotation of breakouts.
Using geomechanical models from a specific field, the effects of in-situ stress, pore pressure and rock properties on formations were evaluated in inducing wellbore instability during drilling operations in a tight gas reservoir. It was found that the most favorable orientation for directional drilling is parallel to the maximum horizontal stress (SHmax) within that field.
The geomechanical study provided inputs not only for wellbore stability during drilling, but also regarding the response of natural fractures to in-situ stresses to become hydraulically conductive (permeable) to act as flow conduits. The fracture model of the field shows that the dominant fracture corridor trend in the field is NNE coinciding with present day in-situ maximum principal stress direction.
Pore pressure prediction for exploratory deep Paleozoic well to avoid kicks, blow-outs, borehole instability and to design safe mud weight during drilling phase is a major challenge due to unavailability of deep well informations in South Fuwaris field, Kuwait. The problem was resolved integrating acoustic impedance volume derived from innovative seismic inversion on Pre-stack 3D Q-Land seismic data and geomechanical model with deeper pore pressure trend from drilled well data.
The Q-land data with exceptionally clean, high signal to noise ratio, reliable amplitude, stable phase and wide range of frequency with high trace density facilitated reliable inversion for prediction of reservoir properties from seismic. The high resolution is achieved through global optimization to a single non-linear objective function, which provides the optimum positioning of the layers and 3D multi-trace damping of the random-noise. The low frequency model, a pre-requisite for seismic inversion was built with densely sampled stacking velocity constraining on seismic horizons and wells.
The most popular Bower's method, accounts for Loading (under-compaction) and Unloading (fluid expansion ) was applied to estimate Bower's parameters by cross-plotting velocity against effective vertical stress for drilled well - "A??. The velocity reversal at Sargelu formation was confirmed with kicks in this well which was also cross validated with nearby Humma wells.
The pore pressure and frac gradient were estimated along proposed exploratory well with the trend developed at known shallower well "A?? which was found to be in conformity with regional trends. The lithology predicted along proposed boreholes in order to design mud weight plug and sanctity was reviewed at Top lithological markers using pseudo porosity logs derived with multi-attributes using neural network technique.
This paper presents an integrated approach of pore pressure prediction for drilling deep exploratory well to minimize drilling risks.
Acharya, Mihir Narayan (Kuwait Oil Company) | Kabir, Mir Md Rezaul (Kuwait Oil Company) | Al-Ajmi, Saad Abdulrahman Hassan (Kuwait Oil Company) | Pradhan, San Prasad (Kuwait Oil Company) | Dashti, Qasem M. (Kuwait Oil Company) | Al-anzi, Ealian H.D. (Kuwait Oil Company) | Chakravorty, Sandeep (Schlumberger)
The deep, sub-salt reservoir complex is tiered with fractured tight carbonate at bottom and top, with the two sub-units of "upper unconventional kerogen?? and "lower inter-bedded kerogen-carbonate?? in the middle. This depositional setting is challenging for horizontal well placement where the thicknesses of respective sub-units are about 50 and 30 feet with varying geomechanical and petrophysical properties. Additionally, this complexity poses limitations in completions and effective stimulation of the Kimmeridgian-Oxfordian reservoirs in several gas fields at development stage in Kuwait.
A horizontal well is placed in the lower sub-unit of the laminated complex of unconventional kerogen and fractured carbonate reservoir as a Maximum Reservoir Contact (MRC) type well. A pilot mother-bore was drilled and logged to identify the lithological properties across the entire vertical domain - facilitates the optimization of horizontal drain-hole placement within the targeted reservoir units.
No wellbore stability issues in drilling were predicted based on the geomechanical understanding where core-calibrated logs from offset vertical wells were considered. However, this modeling method did not have the functionality to integrate the impact of drawdown on the laminated formation which became unstable and collapsed during the short open-hole drill-stem test (DST) plugging the tubing prior to the final completions. An alternative "book-shelf?? geomechanical model was considered at pre-drill stage for predicting the wellbore stability. Once the drilling was completed, the time-lapsed multi-arm caliper indicated the validity of the alternative methodology in predicting the unstable stack of laminations in kerogen-rich strata.
The paper discusses an optimization methodology to enhance the understanding of static and dynamic geomechanical stability through the use of BHI data. Objective of the proposed method is to help improve the effectiveness of completions where wellbore stability due to geomechanical complexity in stacked-pay reservoirs is a primary wellbore challenge in deploying the completions and executing a subsequent stimulation and testing campaign.
North Kuwait had discovered several deep reservoirs during 1960s which were not considered for development production till 2010 because of higher priority given to the major reservoirs such as Mauddud and Burgan. Zubair and Ratawi are two such new reservoirs, taken up for fast track development since last 2 years.
In order to achieve the production target for the asset, ZU/RT need to be brought to production. A complete evaluation of all geological/ Geophysical data was done for all penetration through ZU/RT. All testing results available during the exploratory wells were comprehensively gathered and evaluated. Based on the data, fast track well release, drilling & completion were initiated. The objective was to gain production as well as data to reduce the uncertainty for further development and reservoir modeling work. The initial results indicated tremendous challenges in terms of fluid regime as well as reservoir rock properties.
The production, at the beginning of the project, was zero, which has now been increased to about 20 MBOPD within a year. Integrated team work and calculated risks helped to achieve this milestone.
The paper aims to share the challenges and the lessons learnt during the production delivery from the new reservoirs in North Kuwait.
Geological Background/ Setting
Sabiriyah Zubair is a minor reservoir of clastic type, which was on low priority for development/ production since discovered druing 60s.. This is a relatively small reservoir in terms of size and potential, as compared to other major reservoirs in Sabiriyah field viz. Mauddud & Burgans. However, the accomplished intial tests at two wells (SA-00271 and SA-0278) indicate that the reservoir has mobile oil and can participate to contribute to NK overall production. Currently 7 wells are flowing to Gathering centre at total rate of about 10 MBOPD.
Al-kandari, Ayad M.E. (Kuwait Oil Company) | Al-Baghli, Waleed Jawad (Kuwait Oil Company) | Al-Khaldy, Ali Dawood (Kuwait Oil Company) | Al-Mekhyal, Abdullah Naser (Kuwait Oil Company) | Al-Mutawa, Faisal (Smith Bits) | Maliekkal, Harish (Smith Bits) | Ghoneim, Osama (Smith Bits, A Schlumberger Company) | Saleh, Mustafa
Kuwait Oil Company (KOC) launched North Kuwait Gas Development Project in 2007 to fast track production of gas/light oil from deep HPHT Jurassic reservoirs in six fields. The exploratory wells require a large-hole casing design to isolate problematic formations and allow the operator to reach the deep HPHT target zones with maximum hole size.
One of the most difficult/problematic hole sections is Zubair to Hith, traditionally drilled with 16-in bits. The formations are interbedded and consist of abrasive/pyritic sandstone, reactive shale, limestone and anhydrites with UCS that varies between 5-30kpsi. Historically, to complete the 3900ft section required more than three PDC bits or a combination of 4-5 PDC/TCI.
To reduce costs, the drilling team developed the first slim hole well plan and casing string design to explore Cretaceous formations in Northern Kuwait. The objective would be to downsize the hole section from Zubair to Hith to 9¼-in and drill to section TD with three PDC bits. The production casing would then be run from surface to TD instead of the conventional liner tie-back and cementing process.
The section was completed using the latest motor/PDC technologies in two bit runs saving 55% drilling time and the expense of a third bit. The operation set a new Kuwaiti record for the single longest 7¾-in production casing string (13,625ft) and cementing back to surface. Cement log indicated a good bond over all three zones of interest. The downsizing strategy and change in casing string design saved the operator over $1 million USD compared to a large hole and liner-string design. Production testing in Zubair, Ratawi and Makhul was positive, indicating a significant new oil discovery. The entire operation was completed with zero HSE related complications.
Al-anzi, Ealian H.D. (Kuwait Oil Company) | Rao, Narhari Srinivasa (Kuwait Oil Company) | Al-Ashwak, Samar (Kuwait Oil Company) | Kidambi, Vijay Kumar (Kuwait Oil Company) | Al-ajmi, Neema Hussain (Kuwait Oil Company) | Rao, Jonna Dayakar (Kuwait Oil Company) | Al-ateeqi, Khalid Abdullatif (Kuwait Oil Company) | Al-Mayyas, Rawan (KOC) | Olderman, Allan Stefanic (Kuwait Oil Company) | Acharya, Mihira Narayan (Kuwait Oil Company) | Chakravorty, Sandeep (Schlumberger) | De Keyser, Thomas Lee
Deep, tight carbonate reservoirs of Pliensbachian, Sinemurian, and Hettangian Stages of the mid-Mesozoic Era are becoming very important in the continued pursuit of hydrocarbon prospects in North Kuwait. At present, a total of 21 wells have penetrated the targeted reservoir zones. Of these, 12 have been tested for hydrocarbon production covering a large area of about 1700 sq km. Further, six wells have produced oil and gas, with two deemed commercially successful.
The entire workflow to characterize these reservoirs is focused on delineating faults and associated fractures in individual wells. Detailed seismic study and volume curvature maps, revealed the existing fault and fracture corridors. Sub-seismic faults and subtle reverse faults with fractures were detected by log correlations and borehole image. Due to paucity of cores in these zones, descriptions of cuttings samples were used to identify faults and fracture zones, based on the presence of large euhedral crystals in the midst of cryptocrystalline dolomite, suggesting the percolation of hydrothermal fluids through fractures.
Many of the wells were drilled with an overbalanced mud system, leading to near-borehole porosity and permeability damage to the rock matrix and to the fracture system. Damage to natural fractures intersecting the well can prevent their detection, leading to missed potentially productive intervals. Mobility of hydrocarbons in these tight, fractured carbonate reservoirs depends upon (i) wells intersecting a natural fracture system that is sufficiently permeable and connected to a large volume of reservoir rock and (ii) the near-borehole area not having suffered irreversible damage due to overbalanced drilling. In summary, the proposed reservoirs are very tight carbonates (average 3 pu porosities) and a fracture play is considered to be the key factor in production. Acid stimulation produced multifold increases in productivity. Most of the wells were drilled overbalanced, which has negative impact on the producibility due to formation damage.
The Advanced Collaborative Environment Community of Practice (CoP) was formed in March 2009 at the request of BP senior management to share good practice and promote standardization in the area of wells. Its mandate was one of self-help and leveraging scale but working through influence and consensus, with management support rather than by direct authority. The CoP was also required to adhere to company information technology (IT) standards and technology strategy.
At the time of the CoP's formation, collaborative environments had been commissioned in various company locations worldwide, including Aberdeen; Baku, Azerbaijan; Houston; Stavanger; and Tangguh, Indonesia. In the absence of standardized requirements for Wells' collaborative environments and with an emphasis on innovation, each of these centers had been developed independently, strongly influenced by local ideas, needs, and resources. However, it was evident that connectivity between the different locations and with other disciplines was lacking, and that effort was duplicated.
The CoP currently has more than 30 members, including Wells, subsurface, IT, and well technology from 12 locations worldwide. It meets virtually, involving the widest possible membership in different time zones. It has been instrumental in progressing and communicating standards, supporting the introduction and use of common tools and technology, leveraging members' knowledge and expertise, and helping startups in new areas. Overall, the CoP has been a great success. The paper describes the CoP's evolution, from its formation to the present, and critically examines its achievements, shortfalls, and future goals.
In a rapidly changing technical environment, achieving and maintaining alignment between the diverse stakeholders in a medium to large organization can be challenging. The CoP has earned its credibility and has proved to be an effective means of sharing experience and making good use of scarce resources, both keys for adoption at scale.
Al-Adwani, Talal Fahad (Kuwait Oil Company) | Singh, Sunil Kumar (Kuwait Oil Company) | Khan, Badruzzaman (Kuwait Oil Company) | Dashti, Jalal Mohamad (Kuwait Oil Company) | Ferroni, Gionata (GEOLOG International) | Martocchia, Alberto (GEOLOG International) | Estarabadi, Javad (GEOLOG International)
Production has two components - the subsurface potential and the actual production to feed the export line. In North Kuwait, sub surface potential had never been an issue for any speculation. The most difficult part is to integrate all resources, synchronize with each other and create "wonderful symphony" leading to actual production delivery. Several processes have been developed and matured now to gear up the asset to meet the challenging production target for 2010-11 which indicates a jump in production by about 23% in a single year.
In this effort, major processes to play a key role are: Development Well Subsurface Selection Process to optimize the best wells in terms of potential; New Development Well Assurance Process with Key Opportunities for Improving integration with key service providers to NK Asset such as Drilling Group (rig schedule, materials); Production Operations (Flow line/header connections, process capacity); Water Handling (Flow line/header connections, Water injection Supply capacity); Artificial Lift to synchronize ESP equipment availability in line with the well/ rig availability, Project Management (Flow line installation & rationalization), Learning's from Post Appraisal of Wells drilled in last few years; Surveillance Plan - data acquisition, how new information helps to minimize reservoir uncertainties; Drilling & Completion Programs - appropriate technology choices to meet well and reservoir objectives such as multi-zone needs, rigless access for surveillance or interventions, NCWs and artificial lift requirements.
Post-Macondo world - No abstract available.