This paper presents an alternative solution for gas cloud imaging using full wavefield migration (FWM). The application of FWM method have been applied on both synthetic dataset with gas cloud event and existing field with gas cloud issue. The full wavefield migration is an inversion-based imaging algorithm that utilizes the complete reflection measurements: primaries as well as all multiples, both surface and internal to obtain the total reflections measurement. It combines the primary and higher order scattering reflection from the gas cloud to estimate the true amplitude response below the gas cloud. Successful applications to both synthetic and field data examples demonstrate that FWM improves the imaging illumination and resolution below gas cloud as compared to conventional migration.
Maitra, Shivaji (CGG) | Basir, Fariza F. (CGG) | Ghazali, M. Luqman (CGG) | Ghazali, Ahmad Riza (PETRONAS CARIGALI) | Sapiai, Sarmiza M. (PETRONAS CARIGALI) | Kady, Nabil El (Formerly PETRONAS CARIGALI) | Konuk, Tugrul (Formerly PETRONAS CARIGALI)
Deriving high-resolution velocity models in heavily faulted areas is challenging. This can be further complicated by the presence of gas bodies at multiple depth levels. The use of full-waveform inversion (FWI), given long enough offset and a good starting model, is becoming common practice for resolving near surface gas bodies and high wavenumber velocity variations. Also, FWI can honor azimuthal velocity variations by propagating the wavefield through an orthorhombic medium when calculating the objective function.
In the presence of a principal stress orientation, a WAZ or FAZ dataset highlights the velocity variation with azimuth. If the velocity dependence on azimuth and velocity variations across faults are not properly addressed during wave propagation, they can pose severe challenges to imaging complex fault systems including mis-positioned faults and poor fault shadow imaging. To address these challenges, an orthorhombic full-waveform inversion (Ort-FWI) approach has been used to recover a high-resolution velocity model, addressing lateral velocity variations across faults or due to gas bodies, while honoring the azimuthal velocity variations. We show how Ort-FWI produces a high-resolution velocity model that improves fault focusing and heals fault and gas shadow effects. The combination of these improvements gives a clear uplift in the final seismic image.
Presentation Date: Wednesday, October 17, 2018
Start Time: 8:30:00 AM
Location: 208A (Anaheim Convention Center)
Presentation Type: Oral
Mohamed, Haslina (Petronas Carigali Sdn. Bhd. (PCSB)) | Suhairi, Syazwani (Petronas Carigali Sdn. Bhd. (PCSB)) | Musa, Mustaza (Petronas Carigali Sdn. Bhd. (PCSB)) | Khan, Farhan (Petronas Carigali Sdn. Bhd. (PCSB))
Quantitative analysis of seismic reservoir characteristic through Amplitude Versus Offset (AVO) and Seismic Inversion study is typically carried out to determine the reservoir properties and fluid type. However at shallow depth less than 800m, we often face challenges such as: 1) lack of near offset trace in seismic data, and 2) lack of complete elastic log suite (density, P & S sonic) or poor data quality which make the AVO and Seismic Inversion studies not to be feasible. A possible solution to the seismic data issue is site survey seismic data instead. Site survey acquisition design often has shorter length of short-receiver separation thus enabling to record the near offset traces. New technology of sonic tools are now able to record a reliable compressional and shear sonic logs from an unconsolidated and consolidated sediment. This paper present the results from feasibility study for shallow gas detection using unconventional data input of: 1) new acoustic logging tool (AST) for unconsolidated sediment and 2) pseudo3D seismic data from 2D high resolution site survey acquisition.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: 209A (Anaheim Convention Center)
Presentation Type: Oral
Sheik, S. B (PETRONAS CARIGALI) | Amran, N. Adilah Bt (PETRONAS CARIGALI) | Ripin, M. B M (PETRONAS CARIGALI) | Ai, K. Mei (PETRONAS CARIGALI) | Nayak, S. (PETRONAS CARIGALI) | Idris, M. B (PETRONAS CARIGALI) | Johari, A. B Che (PETRONAS CARIGALI) | Monil, F bt (PETRONAS CARIGALI)
This paper highlights an innovative approach where Multibeam Echosounder (MBES) and sub-bottom profiler (SBP) survey results in addition to conventional seismic data were utilized to demarcate locations for shallow coring. Multibeam and Shallow geochemical studies were planned to further de-risk hydrocarbon potential in frontier exploration areas. Following detailed 2D seismic interpretation, MBES survey area and 100 shallow cores were planned. The interpreted MBES data was used to pin point the final shallow core points. Due to the unfavorable weather window, the survey could not be fully completed. Hence, the remaining area was evaluated by an improvised workflow using preliminary processed 3D seismic data (seabed horizon slice) to fulfil the gap. This allows all proposed coring points to be evaluated. Numerous features like seabed scarps, wave form seabed, seabed mounds, and seabed depressions were identified on top of the observations of a number of active gas seepages and pockmarks. A notably hard seabed was encountered during the seabed sampling operations which resulted in low core recovery. The team effort in improvising a different workflow to identify various sea bed features and also demarcating shallow core location through integrating various geophysical data was very much useful.
Standard seismic processing method of estimating velocity is to remove multiples. In this paper, we utilized multiples that contain valuable subsurface information. A line from a field in the Malay Basin were used to estimate an interval velocity using the Joint Migration Inversion (JMI) method. The motivation for this approach are 1) multiples increase illumination especially in the shallow shadow zones, 2) multiples provide an additional sensitity to velocity errors and 3) the velocity estimation process is automated. In the JMI method, seismic imaging is done in a closed-loop manner as opposed to the standard seismic processing open-loop method. The initial migrated seismic image is feedback to a forward modelling algorithm. This allows an iterative minimization of the difference between the simulated and the real measurements. This also enable velocity estimation to be carried-out simultaneously. The method was first applied on a synthetic data before an application to a real data set from the Malay Basin. The results obtained showed that multiples can be utilized to get an accurate velocity model while at the same time getting a better seismic image of the subsurface.
Malikai development project features Malaysia's first tension leg platform (TLP) installation. The TLP tendon piles were designed by leveraging practice and experience from the Gulf of Mexico whilst taking site-specific earthquake design criteria into consideration. A comprehensive site investigation was performed for site characterization, geohazard assessment, and development of data for facilities design.
The TLP is tethered to the seafloor with eight tendons, each of which is connected to a 2.44 m diameter by 130 m long, 425 tonne foundation pile. Pre-service load cases, including transportation/handling and stability at self-penetration free-standing condition, plus in-place load cases, including hull and tendon damage cases, and earthquake condition, were considered in the design. An extensive seismic design analysis was carried out involving site response analysis to determine the kinematic effect as well as inertia loading on pile design as per ISO 19901-2 based on site specific seismic design criteria.
The TLP foundation piles were installed in May through June, 2016. Actual piling performance observed in the field matched model predictions. The recorded self-weight penetration of all eight piles was within the predicted range. The piles were driven using an underwater hydraulic hammer to a target penetration depth of 124 m and the measured blow-count agreed with "best-estimate" predictions of drivability.
This paper presents the overall design process, including site investigation, the selection of TLP site to avoid geohazards, detailed geotechnical and structural design of piles. Pile installation records and field observations are also presented and compared to pre-installation predictions.
Coal is one of the important resource rocks in Malay Basin. It dominants from Group E to Group I which are the main hydrocarbon reservoirs in Malay Basin. A coal bed is a good indicator in structural interpretation, however the existence of coal interferes the interpretation of seismic amplitude. The coal layer s distort the amplitude and frequency of underlying reservoirs. Thus the hydrocarbon reservoirs lay beneath coal beds are difficult to be interpreted due to the coal masking effect when the reservoirs are close to coal.
This paper discusses the removal of coal seam using matching pursuit in a field of Malay Basin. The reflection of the coal bed is exacted and removed by matching pursuit with a Ricker wavelets dictionary. The result is used for recovering the reservoir masked by the coal bed. This method is good for amplitude interpretation, particularly in the Malay Basin where it is interbedded with coals and hydrocarbon reservoirs.
Presentation Date: Thursday, September 28, 2017
Start Time: 11:25 AM
Presentation Type: ORAL
AbstractThe process to conduct a Biodiversity and Ecosystem Services Risk Assessment (BESRA) was established to enhance situational baseline on biodiversity data for PETRONAS’ upstream and downstream operations, and reducing the impacts on biodiversity in areas of its operation. The location for this assessment was Open Block SK6-00 in the District of Limbang, Sarawak. BESRA consists of a set of questions and a site visit to the identified locations. The template used is developed in accordance to the International Finance Corporation (IFC) Performance Standards, IUCN Conservation Tools, PETRONAS HSE Risk Matrix, and PETRONAS Technical Guidelines: Environmental Management of Oil and Gas Operations in Tropical Rain Forest. Desktop assessment was made on the demographics mapped against the current practices adopted by the Project Management Team (PMT), as well as identification of existing biodiversity risks, and affected stakeholders. Initial discussion with project owners was held to clarify the Terms of Reference and to establishroles and responsibilities. The BESRA specific scope is divided into five (5) categories. These are (1) General Biodiversity, (2) Protection and Conservation, (3) Management of Ecosystem Services, (4) Management of Living Natural Resources, and (5) Supply Chain. During the site visit, photographs were taken for records purposes and short interviews were held with the project team. One of the key findings are the completed transact lines had been 90% restored to an almost pristine condition before the project begin. It was also discovered that the very small number of blast holes that was overblown could cause severe burn for the plants within its five metres radius from the shot holes. However this would prolonged the restoration process but not totally destrying the area. Awareness and improving the management practices is imperative to improve the situation and support the objectives of this assessment. It can be concluded that PETRONAS’ current practice of conducting 2D-Seismic activity for tropical onshore locations is low-risk due to the PMT's proactive stance. The two broad themes identified as solutions includes the inclusion of biodiversity management plan in current procedures and awareness on the locality of the BES in the area. The results of this initiative indicated that awareness on BES issues have improved significantly and consideration is now given to formalise BESRA as part of the procedure for future seismic studies. Furthermore, it has contributed towards PETRONAS’ data bank on terrestrial biodiversity in the area concerned while verifying biodiversity data contained in the EIA. BESRA can further enhance the organisation's internal capacity in conducting such assessment and empowering the employees to conduct their own assessments for continuous improvement thereby reducing reliance on consultants.
Geological interpretation based on the seismic attributes can enhance the accuracy of the interpretation. According to
Yoong, William Liew Sin (PETRONAS Carigali Sdn. Bhd.) | Azmi, Fadzliana (PETRONAS Carigali Sdn. Bhd.) | Rahim, Azral A (PETRONAS Carigali Sdn. Bhd.) | Ghani, Syazwan A (PETRONAS Carigali Sdn. Bhd.) | Idris, M Faisal Rizal (PETRONAS Carigali Sdn. Bhd.) | Idris, M Ramdan (PETRONAS Carigali Sdn. Bhd.) | Ibrahim, W M Syazwan W (PETRONAS Carigali Sdn. Bhd.) | Rahman, Hamdan Abd (PETRONAS) | Sawal, M Rizal (PETRONAS Carigali Sdn. Bhd.) | Wan, Terrence Lawai (PETRONAS Carigali Sdn. Bhd.)
Straits of Malacca Exploration Campaign marks PETRONAS' first oil/gas well drilling in the region of West Coast of Peninsular Malaysia. Three (3) exploration wells were drilled in a period of four (4) months. This paper will highlight the challenges, lessons learnt and key to success of this fast track drilling campaign in a new region of operation.
The team which was entrusted with the mission to drive PETRONAS' quest of oil and gas in this new region were then given six (6) months to deliver the first well out of three (3) exploration wells. Apart from the uphill task to set up staging base and logistics support in the West Coast of Peninsular Malaysia, the team faced challenges of drilling in one of the world's busiest shipping lane. Navigational safety is one of the main concern here. Besides, two (2) of the three (3) wells were located close area where sea robberies and hijacking were rampant. In terms of drilling operation, two (2) of the wells were exposed to the risk of total losses. This paper will share the approaches taken by the project team in overcoming challenges in three (3) main areas - (1) logistics; (2) navigational and offshore safety and security; and (3) well engineering.
Although faced with numerous challenges together with limitation of time and resources, the project team has managed to deliver all the three (3) wells successfully, meeting all the geological objectives within Authorisation For Expenditure (AFE) cost. On top of that, the drilling campaign was completed with zero Lost Time Incident (LTI) and zero accident. Another notable success in this project is setting up the modus operandi in a new region of drilling within six (6) months. Due to the fast track nature of this campaign, first of the three (3) wells was spudded concurrently with 3D seismic interpretation by taking the risk of relying on 2D seismic data. Halfway through the well construction, Well #1 (Well A) was re-sanctioned based on the findings while drilling and latest 3D seismic data received. Target depth of the well was revised to 3130m TVDSS from initial 2100m TVDSS. Despite all the challenges, the drilling team managed to complete drilling operation of three (3) wells ahead of time by 11 days in total.
Apart from engineering and logistics challenges, this paper will share the experience of drilling in one of the busiest shipping lanes in the world. Lessons learnt and key success factors of this fast track exploration drilling campaign will be beneficial to all oil and gas (O&G) operators, especially to those planning to operate in the Straits of Malacca or any other similar regions in the world.