There are five wells planned to be drilled in B field infill campaign starting Q3 2020 - Q1 2021 as per development plan. Two wells are planned to be installed with Digital Intelligent Artificial Lift (DIAL) system, which one in single string completion and another one in dual string completion. This paper will mainly describe on the DIAL application in dual strings completion in B field. The DIAL system has circumferential 3 active orifice valves to open/ close selectively or in combination, which is communicated and operated through TEC cable from surface remotely. Given that this will be the second DIAL system installation in the world, a back up gas lift mandrel (GLM) will be installed to mitigate the risk in case the DIAL system fails to work due to any unprecedented reason so that conventional gas lift valve can be installed in GLM and gas lift operations can be commensed. The world's first DIAL installation in dual strings was completed in a different field offshore Malaysia in Q2 2020. During well completion and system installation, all the DIAL units in short string were functioning well, however there were some issues initially observed in Continuity Resistance (CR) inconsistent reading during run in hole completion and then total failure was observed in long string after its installation based on CR test, TDR (Time Domain Refractometer) test, and Scope Test due to unprecedented technical issue which affected the downhole cable to receive and send electrical signal to operate DIAL valves. The risk assessment has been conducted with associated parties based on the failure analysis and lessons learnt from the first DIAL application in dual strings in order to implement mitigation plan and proceed with DIAL application in B field. This step is very crucial to build the learning curves as well as improve the operator's understanding on for future DIAL application in dual strings. This paper will summarize the DIAL tool functionality and its design, failure analysis & lessons learnt from other field offshore Malaysia, and risk assessment & mitigation plan carried out for the DIAL application in dual strings in B field. It marks the second application in the world at present & first successful DIAL application in dual strings worldwide presently.
The economic value of completing a reservoir is strongly influenced by the fluid type. Wells drilled in developed brown field penetrate reservoirs with significant pressure loss due to offset production. A major challenge in evaluating mature reservoirs is the uncertainty introduced by pore fluids with unknown or varying petrophysical properties, such as change hydrocarbon gravity, diminishing pore pressures, and low to absent gas level indication. These are prone to error and uncertainty. Accurate understanding of reservoir fluid properties is therefore a key requirement for successful reservoir management. This manuscript illustrates a successful integrated workflow to ascertain. An integration between LWD triple combo data, near/far neutron, mud logs, pressure measurement, and production history of neighbouring wells, are critical to confirm fluid type within the drilled reservoirs. Cross plots, ratios and confidence analysis are required to ascertain the confidence level. Acquired data was ranked according to uncertainty associated with the acquisition technique, rate of penetration, lag time, mud type, and pre-test drawdown. Mobility was used as an indicator of fluid type or phase change in absence of any major rock type changes. Gas data were verified for any mud contamination and analysed using ratios to verify Hydrocarbon wetness. Data was ranked based on confidence factor determined through data precision and reservoir propertied. We also highlight the uncertainty in measurements. The fluid typing workflow used successfully identified the correct fluid typing, and reduced the reliance on single conventional method, or the need to run pre-test measurements. Data in intervals dominated with residual oil saturation showed misleading fluid type, same applies in high permeability sand, corrected gas data analysis gave a good indication of fluid type and mapped the change in fluid phase when combined with log data, while near/ far neutron aided to correlate the different sands, however due to its relationship with porosity, there is no one correlation could be derived. This paper illustrates that standard petrophysical techniques, such as analysis of density and neutron porosity logs, near/far neutrons, pretest can give misleading results if used in solo without consideration to the uncertainty associated with the measurement. The integration of fundamentally different data has resulted in identifying the fluid typing and its distribution in the reservoir and without integrating other measurements. A fluid typing systematic was developed to ensure the best and cost-effective model to assure the correct fluid type is identified. In this paper, a methodology is proposed which uses the geodesic transform, and integrate various source fundamentally different data, which is routinely acquired, then develop a systematic reasoning of confidence on data precision and accuracy. The system followed ensured the correct mapping of fluid typing in various reservoirs with different petrophysical properties. It is the first time such workflow is followed, and an integrated approach is consistently used in different sandstone reservoirs.
To appraise hydrocarbon and its properties of a low permeability formation within deep Baram delta reservoirs. Formation X is low permeability silty sandstone. It forms along other formations stacked sandy shale reservoirs. The stacked formations are interpreted as Hydrocabon bearing formations based on the openhole and pressure data. However, the reservoir in question, showed features different from the adjacent reservoirs. This manuscript appraises the reservoir and illustrates the workflow followed to identify its fluid type and the best method to produce the hydrocarbon. Triple combo logs identified formation X as hydrocarbon bearing with low permeability and low porosity. Formation pressures gradients indicated the formation to be oil; however, the bottom hole sample, when pumped out, indicated alternating of oil and gas despite the low differential pressure. During the PVT measurement the sample was first re-pressurised until a single phase was achieved and it was then subjected to Differential Liberation and Constant Composition Experiments (CCE). These experiments showed the Bubble Point pressure of the sample to be higher than the reservoir pressure, thereby indicating two mobile phases in the reservoir and the probability of a Gas-Oil Contact (GOC). The Experiments were also successfully simulated and matched using the Peng Robinson Equation of State. The Laboratory experiments directly contradicted the interpretation of Wireline Logs and pressure gradient both of which, indicated single phase light oil. The collected bottom hole sample indicated that both oil and gas are mobile at reservoir level, this finding is supported by PVT laboratory experiments. The Differential Liberation, CCE experiments and EOS fitting demonstrated the fluid to be two Phases at Reservoir Condition where both phases are likely to be mobile. Therefore, it is suspected that the fluid will go from being Gas to Oil with increasing depth without going through GOC, i.e. with continuous compositional grading as is possible for fluids near their critical temperature. This phenomenon could not be captured using open hole conventional logs and therefore the is team is currently investigating the best practice to identify such reservoirs.
Coring and core analysis are considered the only direct and physical data to provide a true reflect to the reservoir properties. The measured properties are used to calibrate subsurface models and ensures close to reality properties. Representative data is critical to allow achieving such target. Coring planning and close follow up from the day decision is taken to core is important to achieve representative data. The approach followed in this manuscript allowed a high probability of successful core cutting, and representative core analysis. Field A is planned for appraisal phase and reservoir is expected to be of low permeability with sequence of shaly sands which adds complications to achieve the objective in cutting and analyzing the core. Different coring technologies were evaluated against the main coring objective of potential hydraulic fracturing field development. Conventional core is selected to offer the best value in both cost, and data coverage in compare to sidewall core. However, due to financial impact only one run was allowed, consequently it was critical to get the highest possible recovery and highest quality in one shot. An extensive planning phase investigated all variables to ensure high recovery. Rock strength and its mechanical properties allowed the selection of optimum coring parameters, coring accessories, and coring bit. It is critical to the project to collect the core and the added challenge of only single run required detailed workflow. Borehole size, mud wt, rate of coring and coring parameters were challenging due to the given one time opportunity. As a result, successful 100% core recovery is achieved, core retrieval to surface ensuring least core damage, this is demonstrated by CT scan which indicated no tripping out induced fractures. Well site core preservation reduced any weathering alteration, the selected stabilization method allowed minimal invasive to the core. Electrofacies guided by the whole core CT scans allowed the best coverage to the reservoir's properties. Long and large diameter plugs were achieved. Cleaning pilot study facilitated the selection of least damaging cleaning and drying method. Pilot small core analysis programs, and close follow up, and the analysis of raw data reduced the risk of unrepresentative core analysis results. Conventional core analysis data allowed refining and enhancing premeasurement electro facies and allowed a distinctive rock typing. The detailed planning permitted us to secure 100% core recovery and ensured core is reached the surface with least possible damage. The followed core analysis strategy reduced redundant experiments and allowed representative results at the same time optimized on the cost. This paper demonstrates the best practice that is followed in challenging environment of shaly sand sequences to successfully cut core and develop a program, and workflow which reflects the uncertainties to be solved.
Acquiring acoustic slowness data in open & cased hole and a reliable cement bond log in one run without jeopardising data quality or increasing rig time is desired for fast and optimize data acquisition. This paper reviews the steps taken to ensure acoustic slowness and cement bond data acquisition fulfils the objective, while minimising the cost in an offshore challenging environment for formations with variable acoustic velocities that could be masked by strong casing arrivals. Crossed dipole acoustic logging is typically preferred to acquire within open hole environment for best quality signal. However, due to drilling challenges this could not be done in the subject well. Data was acquired in 6in open hole and 7" liner (8.5 in Open hole behind) cased hole section together in one run. Shear slowness in slow formation requires propagation of the low frequency dipole flexural wave whereas compressional slowness acquisition and cement bond evaluation requires high frequency monopole data. An improved understanding of cased-hole acoustic modes allowed developing the ability to transmit acoustic energies at optimal frequencies in order to acquire formation slowness concurrently with cement bond. Acoustic data quality in cased hole is dependent on cement bond quality. Poor bonding or presence of fluid between casing and the formation inserts noise in the data by damping the acoustic signal. Hence, understanding of the cement bond quality is critical in interpreting the cased hole acoustic data. The low amplitude of the compressional first arrival indicated the presence of cement bonded with the casing. Absence of casing ringing signal at the beginning and presence of strong formation signal in the VDL indicated good bonding of cement with formation. Filtration of the cased hole acquired semblances were necessary to remove the casing and fluids noises. Acquired data shows good coherency and continuous compressional and shear slowness's were extracted from the good quality semblances. This integrated strategy to acquire the formation slowness and to evaluate the cement bond quality and top of cement allowed meeting all objectives with one tool in single run. The risk of casing waves that could have masked the formation slowness signal was mitigated by transmitting acoustic energies at optimal frequencies with wider bandwidth followed by the semblance processing. The effects of borehole ovality, tool centralization, or casing centralization on waveform propagation were studied to supplement the interpretation. The first times strategic logging application in PETRONAS allowed time and cost saving and fulfilled all data acquisition plan. Data quality assurance and decision tree allowed drafting a workflow to assure data quality. This solution showed importance of smart planning to maximise advanced tools capabilities to acquire acoustic slowness data and cement evaluation in single run in offshore challenging environment.
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