Influenced by the success of shale gas production worldwide and to meet requirements for clean energy supply, a multidisciplinary team of petroleum specialists was established in Saudi Aramco. Meeting the growing requirement in industrial consumption and especially electricity production is a driving force for developing unconventional gas reserves. "The initial focus is in the northwest and in the area of Ghawar, where gas infrastructure exists. Initial knowledge building from similar plays in North America is being supplemented with internal technical studies and research programs to help solve geological and engineering challenges unique to Saudi Arabia and to locate specific wells planned for 2011. The company is innovatively combining knowledge and research to maximize gas reserves and production from conventional and unconventional resources in order to meet growing domestic demand" (1). During years 2010 -2011 major international petroleum industry players -Schlumberger, Halliburton and Baker Hughes -were invited to share their experience in a series of workshops held in Dhahran. Exchange of expert ideas developed into appreciation of complexity of the shale gas reservoir and helped to identify the scope of work for the first Silurian Qusaiba shale gas well. The SHALE-1 well was drilled in 2007 as a gas exploration well. Recent drilling and geophysical data obtained in the well were beneficial for detailed sidetrack and fracture stimulation design. The Multidisciplinary Saudi Aramco -Halliburton SHALE-1 task group was established and positioned in Dhahran. This allowed them to have regular face-to-face meetings and improve the most critical criteria of any new venture -communication. The draft work plan was developed 8 months before actual operations commenced on the well site. Thorough examination of the draft work plan progressed to the final work plan with a number of improvements. For example, "R" Nipples were dropped from the monobore 4-1/2" completion string. The Frac Stimulation design was fine-tuned, involving expertise from Saudi Aramco and Halliburton. The Complete Well on Paper exercise involved over 25 specialists from both companies and helped to rectify remaining completion/stimulation design issues, and put everyone on the same page in terms of the work program. Well site operations commenced in May 2011; the well was successfully re-entered and window cut in 7" liner. An S-shaped 5-7/8" hole was drilled in the direction of minimum horizontal stresses, to the required depth in Qusaiba Shale with a maximum DLS of 4°. The well was completed with a 4-1/2" cemented liner and monobore 4-1/2" string to surface. The Hot Qusaiba interval was perforated, frac stimulated with mixed results, and successfully flowed. A temporary isolation ceramic (easily drilled) plug was set above the perforation interval. The Warm Qusaiba interval was perforated, successfully frac stimulated, and flowed with mixed results. Finally, the plug was drilled out with CTU and both intervals flowed and required production log...
Influenced by the success of shale gas production worldwide and to meet requirements for clean energy supply, a multidisciplinary team of petroleum specialists was established in Saudi Aramco. Meeting the growing requirement in industrial consumption and especially electricity production is driving force for developing unconventional gas reserves. "The initial focus is in the northwest and in the area of Ghawar, where gas infrastructure exists. Initial knowledge building from similar plays in North America is being supplemented with internal technical studies and research programs to help solve geological and engineering challenges unique to Saudi Arabia and to locate specific wells planned for 2011. The company is innovatively combining knowledge and research to maximize gas reserves and production from conventional and unconventional resources in order to meet growing domestic demand." [1] During years 2010 – 2011 major international petroleum industry players – Schlumberger, Halliburton and Baker Hughes – were invited to share their experience in a series of workshops held in Dhahran. Exchange of expert ideas developed into appreciation of complexity of the shale gas reservoir and helped to identify the scope of work for the first Silurian Qusaiba shale gas well. The SHALE-1 well was drilled in 2007 as a gas exploration well. Recent drilling and geophysical data obtained in the well were beneficial for detailed sidetrack and fracture stimulation design. The Multidisciplinary Saudi Aramco - Halliburton SHALE-1 task group was established and positioned in Dhahran. This allowed them to have regular face-to-face meetings and improve the most critical criteria of any new venture – communication. The draft work plan was developed 8 months before actual operations commenced on the well site. Thorough examination of the draft work plan progressed to the final work plan with a number of improvements. For example, "R" Nipples were dropped from the monobore 4-1/2" completion string. The Frac Stimulation design was fine-tuned, involving expertise from Saudi Aramco and Halliburton. The Complete Well on Paper exercise involved over 25 specialists from both sides and helped to rectify remaining completion/stimulation design issues, and put everyone on the same page in terms of the work program. Well site operations commenced in May 2011; the well was successfully re-entered and window cut in 7" liner. An S-shaped 5–7/8" hole was drilled in the direction of minimum horizontal stresses, to the required depth in Qusaiba Shale with a maximum DLS of 4°. The well was completed with 4-1/2" cemented liner and monobore 4-1/2" string to surface. The Hot Qusaiba interval was perforated; frac stimulated with mixed results and successfully flowed. A temporary isolation FasDrill plug was set above the perforation interval. The Warm Qusaiba interval was perforated; successfully frac stimulated and flowed with mixed results. Finally, the FasDrill plug was drilled out with CTU and both intervals flowed and required production log runs. All targets set for the SHALE-1 re-entry well were successfully achieved and the well was suspended for future utilization as an observation well.
Subsurface anomalies can present complex well construction challenges. These anomalies to name a few are irregular wellbore stress profiles, low fracture gradients that require complex mud programs and, in some cases, total fluid losses while drilling. Poor wellbore stability is a common result of such anomalies and service companies serving the industry develop technologies to address, mitigate against and overcome these issues. A gas well encountered such a challenge. While drilling the 17″ section complete fluid losses were encountered. These losses generally uncommon in the field and were attributed to a seismic anomaly. This resulted in poor wellbore stability and led to multiple lost BHAs and sidetrack attempts. The surface casing design did not allow for extensive remedial options so rather than continuing recovery operations it was decided to suspend well construction and spud an offset well 50 meters away. Equipped with the knowledge of the drilling problems from the direct offset, the potential problems they represent and considering the proximity, it was decided to introduce two engineered solutions to mitigate against these challenges and secure successful well construction. First, the surface casing design was modified and the 18-5/8″ casing was set deeper and second, casing while drilling (CWD) technology was introduced to drill for 13-3/8″ intermediate casing from the 18-5/8″ shoe to 13 3/8″ casing point (CP). During planning it was concluded that casing drilling technology would allow to simultaneously keep every foot drilled behind casing, under total losses conditions. Furthermore, CwD would minimize the open hole time compared to conventional drilling practices, an important factor when mitigating against risks from poor wellbore stability. Approximately 4.5 days after setting the 18-5/8″ surface casing, a 16″ CwD drill bit made-up to 13-3/8″ casing successfully drilled 1575 ft with total losses and cemented in place across an interbedded formation. This was a starkly different result compared to the direct offset where operations were suspended after many more days between setting the 18-5/8″ to decision to suspend.
Increasing efficiency and safety of drilling operations requires proactive planning and ability to make timely educated decisions. Evaluating operational experience and statistically organizing available drilling data provide valuable forecasting tools, which help to increase the rate of successful decisions. For this paper, drilling records from 54 recent wells drilled by Saudi Aramco exploration unit throughout 2009-2011 period, both offshore and onshore, were evaluated. Large volume of statistical data related to drilling fluid losses was systemized. Losses were tagged as partial and total losses for each well and hole size. Drilling fluid daily reports provided insight into volume and cost of losses for drilled hole sections. Fluid losses cost per foot and lost time cost per hour was calculated. Cost per foot of LCM and cost per foot of other fluid loss preventive techniques and technologies was estimated, as well. This data analyses led to the capability of benchmarking expected losses cost per foot against expected cost per foot of available fluid loss fighting or preventive materials and services. Obtained numbers provide straight forward decisive data to plan for cost effective solution using a decision flowchart. Available statistical and risk evaluation software adds to the decision process effectiveness. This paper does not cover all available or would be available loss prevention techniques and technologies. The discussed method was applied in real life, and aerated drilling fluid services are contracted for Saudi Aramco drilling operations.
Rotary/motor drilling operations amount to approximately 30% of total time of well construction or approximately 800 hrs for gas wells studied in this paper. Reducing drilling time by 10% will result in significant time and cost savings, especially if drilling deep horizontal wells. Time and cost reduction becomes particularly valuable when no extra investments in new tools or materials are required. Optimizing the drilling process using real time feedback from drilling rig sensors is one of the options proved successful by long time practice. Artificial intelligence and its tool: neural networks (NN) is justifiably in the petroleum industry's focus to deliver valuable results with a high return and minimum or no investments. The fact that rock hardness reflects on some drilling parameters is well known. It is natural to try and learn how and to what degree rock hardness can be predicted with use of NN, drilling parameters and well logging records. It is also well understood that the smaller the geographical extent of the formation data sample, the more correlation in properties is observed. This study focuses on wells drilled in the same gas field and cased with the same casing design. This paper summarizes the study of predicting Unconfined Compressive Strength (UCS) while drilling a horizontal well in highly compacted, cemented sandstone with low permeability and low porosity reservoir (unconventional reservoir) with trained NN in MATLAB environment. Methodology and workflow of arriving at the results of the study is provided in extensive details. The initial goal of UCS prediction with NN is to prove the feasibility of proposed workflow and develop a MATLAB function that predicts UCS, utilizing drilling parameters recorded by mud logging unit and drilling rig's sensors and computing expected rate of penetration (ROP) using common published formula. The final goal of the study is to benchmark actual ROP with forecasted ROP with a high degree of certainty (more than 80% correlation), detect drilling troubles, and optimize drilling parameters for balanced performance and safety operations while reducing drilling time for the given footage. The study substantiate the proposed methodology and workflow predicting UCS of the formation being drilled and provides input for comparing predicted and measured drilling parameters. The study also verifies and selects which drilling parameters have substantial correlation with UCS. Keeping in mind that it is important to optimize the optimization process. Reducing the number of input parameters for the NN model was also a focus of this study. It was found that surface coordinates, measured depth, rate of penetration, rotation speed, surface torque, surface weight on bit, gamma ray and depth related logged measurements of UCS are sufficient to train the NN model with R2=81%. Data from 9 wells was used in this study.
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