The targeted reservoir for foam mobility control is usually layered or heterogeneous. However, a major limitation of existing foam models is that there are no dependencies of the foam modeling parameters on permeability, even though the permeability is accounted inherently only through changes in gas-water capillary pressure and shear rate. This results in considerable errors in predicting the foam mobility at largely varying permeabilities, which prevents users from simulating correctly the conformance achievable with the help of foam in heterogeneous reservoirs.
Developing a foam simulator with systematic permeability-dependencies of foam properties is a key enabler for the rigorous simulation of foam floods in the field. An advanced population-balance foam model has been developed with reasonable physical mechanisms associated with the effect of permeability on the bubble density, foam generation and stability in porous media. The derivations indicate that the gas viscosity scaling constant increases with permeability exponentially, while the upper limit of foam texture, the foam generation coefficient, and the limiting capillary pressure decrease exponentially as the permeability increases. All these factors collectively affect the foam mobility. The upper limit of foam texture and the foam generation coefficient share the same power-law exponent with permeability because of the similar fundament. As a result, three additional power-law exponents are needed to correlate with permeability in the new model.
To verify the correlations of the parameters with the permeability change, an automated regression program was applied to fit the resistance factors of several groups of foam flood experiments with foam quality scans at different permeabilities. The newly developed permeability-dependency functions showed its great competency in matching all the experimental data in a wide range of permeability. The optimized parameters are largely consistent with the theoretical exponents of the power-law functions of the aforementioned physical properties correlated to permeability, but also suggest extra modifications. In particular, the exponent for the limiting capillary pressure is about -0.5, which is equivalent to that the limiting water saturation is approximately independent of the permeability according to the Leverett J-function. As a result, the new functions of permeability dependencies for the foam-model parameters in the population-balance model enables the foam modeling with only a single input of foam parameters at a referenced permeability. A 2D layered reservoir case was used to test the new permeability functions, which shows the significant difference in terms of the oil recovery and the injector BHP between whether considering the permeability effect or not.
This paper proposed, for the first time, a systematic methodology to account for the critical permeability effect to simulate foam flooding in heterogeneous reservoirs. This is a key advance in consideration of the major limitation of existing reservoir simulators using fixed or ad-hoc foam-model parameters throughout the entire reservoir. This new model enables the reservoir engineers to simulate and optimize the foam performance in real fields with better accuracy of foam physics in porous media.
Hao, Qian (Exploration and Development Research Institute & Science and Technology Department of Changqing Oilfield Company, CNPC) | Wang, Jiping (Exploration and Development Research Institute of Changqing Oilfield Company, CNPC) | Han, Dong (Science and Technology Department of Changqing Oilfield Company, CNPC) | Li, Wuke (Exploration & Development Research Institute of Changqing Oilfield Company, CNPC) | Liang, Changbao (South Sulige Operating Company of Changqing Oilfield Company, CNPC) | Dai, Libin (South Sulige Operating Company of Changqing Oilfield Company, CNPC) | Jia, Yonghui (South Sulige Operating Company of Changqing Oilfield Company, CNPC) | Qi, Congwei (TOTAL) | Zhai, Gaoqiang (TOTAL)
South Sulige operation project is an international cooperation development of tight sand gas field located in the Ordos Basin, Northwest China. The economy of the project relies on technical breakthrough to select good drilling location for getting higher Estimated Ultimate Recovery (EUR) rather than partners continually reducing annual investment and cost saving to survive in the global oil price fluctuations in the long run.
Although a total of 306 wells have been drilled and 1648 Km2 of 3D seismic data have been acquired and processed during the past 3 years, well drilling results were not as good as expected in terms of seismic sand thickness prediction and channel sand / shale discrimination. Seismic data quality indeed improved due to large efforts of the processing, even getting clear seismic images at reservoir level, however, at Upper Permian He8 Formation, the main gas producing target layer, seismic interpretation results are still difficulty to distinguish complicated fluvial depositions of this tight sand gas filed.
On the other hand, existing production data indicate that Absolute Open Flow (AOF) of the super good well which accounts for only 3% of the total drilled wells usually exceed 120×104m3/d, annual production of the super good well could exceed 2500 ×104m3, EUR of the super good well may exceed 2.4×108m3. Compared with the ordinary well, EUR of the super good well is 9.6 times that of the ordinary well. As a result, accurate predicting good drilling location and try to capture more super good wells remains the biggest challenge and the most attractive research direction for this international cooperation project.
Therefore, a different approach joint 3G (Geophysics, Geology, Gas Reservoir) integrated study is carried out by an international joint research team from Paris, France and Xi’an, China. This paper shows a new method of combining sedimentological model from wells results (static data include core description, typical channel E-logs parameters, semi-regional synthesis. dynamic data include AOF, annual production, EUR) with low value of Poisson's Ratio (PR) / amplitude maps which were defined in the study, aiming to identify areas where a given dominant fluvial facies could be predicted.
The paper's objective is to share the integrated study approach to get better understanding of such tight sand reservoir, and the proposed methodology opens new opportunities for predicting good drilling location, increase the probability of capturing more super good wells, lower the project development risk with best practices approach.
This paper provides technical feedback of a successful use of Directional Casing While Drilling (D-CwD), a technique allowing to simultaneously drill and case the hole while following the directional plan. It highlights how substantial gains were realized on Badamyar project in Myanmar, having benefited from the D-CwD technique to optimize the architecture.
The Badamyar development campaign involved the drilling of four horizontal gas wells in conventional offshore environment in Myanmar. Other regional wells had already experienced wellbore issues to get the 13 3/8″ casing vertically to 450m. On Badamyar, drilling directly with the casing allowed to minimize operational exposure to losses and wellbore instability, and to achieve the challenge to get the 13 3/8″ to 800m and 45deg inclination, avoiding the requirement for an additional surface casing.
All four 13 3/8" sections were successfully directionally casing-drilled and cemented in fourteen days within budget duration, which, despite the additional complexity, is comparable to the best performance in the block in the last twenty years. The average Rate of Penetration was 30 m/hr, same as fastest conventional case in the field, without mentioning the huge advantage that when reaching the required depth, the casing is already in the hole. Indeed, once the casing has reached the required depth, drill pipe is run inside the casing to unlatch and recover the directional BHA, and pull it back to surface, leaving the casing in place ready for the cement job. While conventionally, casing still needs to be run with associated time and risks (losses, wellbore stability, stuck casing, accidental side-track, etc…).
This Directional-CwD was a new concept to most of the teams involved: Operator, Rig contractor and Tubular Running Services. It required changing the "hundred and thirty years of conventional drill-pipe drilling" mindset. This paper describes the decision making process to switch from conventional to casing-drilling, the preparation phase where risks were identified and mitigated, as well as the excellent operational results.
This paper, by presenting a successful first implementation within a major O&G company, brings to the drilling industry an additional case that the system works, is technically fit-for purpose, cost effective, and has the tremendous potential to replace conventional drilling in several applications. It also highlights some potential limits and opportunities for optimization which should be considered for further development (trajectory constraints, fatigue life and well control).
To minimize capital costs, operating companies are choosing to produce oil and gas through longer and longer subsea tie-backs. Transportation of multiphase gas, oil and aqueous mixture over long pipelines under high pressure and low subsea temperatures present some unique challenges. One of the most important challenges in flow assurance for such more common long pipeline designs is the possibility of blockage due to hydrate formation and/or wax deposition.
This paper discusses results using the newly developed wax deposition and hydrate transport models for a pre-FEED study. The models demonstrated are integrated into a generic and well proven multiphase dynamic simulator framework designed to be used for pre-FEED and FEED studies for a green oil field as well as to trouble shoot production challenges and simulate production of an already producing field.
LedaFlow™ is the multiphase, transient simulator that was used during the study. It contains a framework which easily allowed implementation of the new modules for wax and hydrate.
Wax deposition and hydrate transport are two important challenges for pipeline design and operations with waxy oil fluids that are prone to hydrate formation. An accurate model for quantifying the wax deposition and hydrate transport processes is essential to assure secure and safe transportation of these hydrocarbons. In addition, providing accurate predictions of not only the pressure drop along the pipeline but also of the flow behavior during the transport will help to optimize the development schemes, avoiding over-design. There are several options for modeling both processes, however, for the evaluation reported here not only the process itself is important, but to model dynamic operational scenarios is also important. For this study a waxy and hydrate forming stream was selected. This stream comes from a single stage separator in an offshore facility.
The new wax model includes some key features, such as the non-Newtonian nature of the waxy oil, the growth of the wax layer and the effect on heat transfer throughout the pipeline. It is based on a known model from the literature, however, it brings a fundamental new framework for simulating the effect of wax on multiphase flow as it benefits from all the functionalities of the multiphase flow simulator like transient operations, accurate thermal modeling including use of heat tracing. All of this has been considered in our study of normal operations. In the hydrate transport model, mass transfer during hydrate formation, the hydrate former/water depletion in the pipeline and the slurry viscosity with hydrate particles have all been considered.
The recent major seismic events in South East Asia have led the Oil & Gas Companies to reevaluate the design of their offshore platforms with sometimes more stringent seismic conditions than original ones. The Yadana offshore platforms located in a high seismic activity area in the Andaman Sea, operated by TOTAL E&P MYANMAR, were part of this important work. DORIS Engineering and GDS have developed specific seismic analyses to validate the design under new conditions.
This paper will present the different engineering challenges which were faced to revalidate the structural integrity of the different jacket type platforms under new seismic conditions. It will describe the methodology specifically developed for this project and how were identified and defined the necessary site modifications. These analyses were developed to assess more accurately the maximum relative displacements of jacket type platforms connected by bridges and to validate the stresses in foundation piles. It will also address the offshore works performed on the platforms with a maximization of SIMOPS works and limited shut down periods.
Insufficiencies in the conventional design approach required to develop specific methods to validate the integrity of the jacket foundations and the platforms displacement (bridges). This paper will address, in particular, the design methodology used to verify the integrity of the jacket foundations and to define the required topsides and jacket reinforcements. A time domain approach, based on the "ASN" guidance used for nuclear facilities, was developed to verify the pile stresses and assess more accurately the maximum relative displacement of the platforms connected by bridges. The offshore works were afterwards performed in a timely and cost-effective manner. The detail engineering and the operation offshore had to include risky and unconventional operation such as bridges pot bearings replacement or piping modifications on bridges. SIMOPS works were maximized allowing the shutdown to be limited to the shortest duration.
This paper presents the different engineering challenges which were faced to revalidate the design of existing platforms. It presents the specific methods which have been successfully developed by engineering to validate the design. This project is a good example of a "brownfield" project, from a challenging situation through development of a reliable and efficient engineering solution to successful completion of offshore works.
This paper describes 4D interpretation results in a very challenging Middle East carbonate context.
It consists of a 4D pilot (OBC/OBC) over a giant field divided into two phases. For Phase1 the monitor seismic survey has repeated the geometry of the base survey (parallel shooting) to get started in the best possible 4D conditions. For Phase2 the monitor seismic survey design is a modern source spread acquisition for wide azimuth objective. It is clearly different from the base survey design, and so starts with a worse 4D repeatibility.
In this paper, we describe the challenges attached to both phases of this pilot and explain how in the end it has been successfully interpreted.
A focused study is made on a particular 4D anomaly corresponding to an increase of impedance in the reservoir. This is interpreted as the water front movement (due to water injection) during the interval between base and monitor surveys. Petrophysically this is consistent, if water replaces oil in the reservoir then impedance increases. However, 4D interpretation can be ambiguous and other production phenomena can explain impedance increase, so the interpretation must be assessed carefully. This is done through calibration of the interpretation to well data (time evolution of the water cut).
The final interpretation is robust. Other elements not described in the paper could have been added to consolidate the interpretation like the fact that interpreted 4D anomalies (and so water rise-up) stop vertically on a well known impermeable barrier (anhydrite level).
Once the 4D signal is calibrated, unexpected phenomena (i.e. heterogeneities not predicted by the reservoir model) are highlighted as potentially providing added value to reservoir understanding. As a deliverable, 4D anomalies are interpreted as 3D geobodies and a water rise-up top surface is picked. This information will be key to position new wells and to update the reservoir model.
Though 4D seismic techniques are very mature and widely illustrated in clastic reservoir environments, it is still rarely used operationally to monitor carbonate fields. This paper proves the concept that a reliable 4D signal can be extracted over such Middle-East carbonate reservoir.
Summary Total EP Bolivie carried out two Magnetotellurics (MT) surveys in the bolivian fold belt of the sub-andean foothills. These surveys were aiming to estimate the local absolute depth of the Los Monos/Huamampampa (Devonian) resistivity interface at depth about 5-6 km, and map the relative geometry of this resistivity interface. To achieve this goal, MT was extensively analyzed with a dedicated workflow. First, data quality was assessed; then, the most up-to-date geological interpretation was introduced in sequential 2D/3D unconstrained & constrained inversions; the last step was the updated HMP interpretation from the results of 2D and 3D inversions. The foothills of Southern Bolivia are characterized by a succession of sub-parallel NS trending mountain ranges, which correspond to a tightly folded elongated anticline structure, predominantly composed of clastics sediments.
Keogh, William (University of Leeds, Leeds) | Charpentier, Thibaut (University of Leeds, Leeds) | Eroini, Violette (Statoil ASA) | Olsen, John Helge (Statoil ASA) | Nielsen, Frank Møller (Statoil ASA) | Baraka-Lokmane, Salima (TOTAL) | Ellingsen, Jon Arne (Conoco Phillips) | Bache, Oeystein (Conoco Phillips) | Neville, Anne (University of Leeds, Leeds)
Deposition of inorganic scale on downhole completion equipment contributes to significant downtime and loss of production within the oil and gas industry. High temperature/high pressure (HT/HP) fields have reported build-up of lead sulfide (PbS) scale as a consequence of reservoir souring. This paper reports on the design of an experimental rig allowing diffusion of H2S into a scaling brine under dynamic environments. Multiphase conditions induced by introduction of a light distillate within the system were used to create an emulsion in order to reflect more accurately the scaling process occurring within sour systems. The results showed that the presence of an oil phase within the system caused the lead sulfide nano crystals to reside at the oil- water (o/w) interface; increasing surface build-up propensity through an adhesion process. Performance of a range of coatings for potential application in oilfield environments was determined through gravimetric measurements and microscopy techniques and the wettability of surfaces was shown to have a significant influence on the degree of lead sulfide deposition in a multiphase system.
One barrel of seawater has to be injected into the reservoir in order to be able to produce the same amount of oil. In order to avoid problems of souring and/or incompatibility with reservoir water, desulphated seawater is injected.
In this paper, we have completely reconsidered the desulphation process with the objective of producing more water while optimising the quantity and type of scale inhibitors, with a priority given to green chemicals. The desulphation process established since 1992 has not been modified since. Our new philosophy adapts to the constraints of the field life. Theoretical and simulations studies have been carried out on risks of scale deposition on the membrane (polarisation layer) taking into account parameters and physical laws based on fluid mechanics, electroneutrality and material transfer. The behavior of membrane and risk of deposition depends on temperature, pressure, flux, tangential flow, potential accumulation of scale on the membrane and spacer; site and laboratory pilots have been used. Tube blocking tests have been carried out in order to select the scale inhibitors. Results showed that it is possible to operate beyond 80% of recovery with the help of a scale inhibitor. 83% recovery appears to be a maximum limit. Without the use of a scale inhibitor it is possible to obtain 75% of recovery under certain circumstances.
These results have enabled us to issue operational recommendations on TOTAL operating fields, on projects under development and on our future projects. The increase of the recovery and / or decrease in the concentration of scale inhibitor will conduct to less chemical discharged to the sea (via the concentrate). In addition, the selection of scale inhibitors has allowed selection of several biodegradable products, with better efficiency than currently used products. Of the 11 products tested, four have been selected. Reduction of OPEX: The consumption of scale inhibitor could be reduced by 2 or 3 and even suppressed for certain operating conditions. Selection tests have allowed us to choose most appropriate chemical from a technical, economic and environmental friendly point of view. Reduction of CAPEX: The increase of recovery has allowed us to reduce the dimensioning of the whole pretreatment of the nanofiltration as the flowrate is the parameter that influences the most the cost of a water treatment plant.
Smart water injection or low-salinity water flooding is an enhanced oil recovery technique for fractured reservoirs. The mechanism of low-salinity water flooding is performed by altering the wettability of rock towards water-wetness. This study presents an evaluation of low-salinity water flooding based on a brown field fractured reservoir properties by using explicit simulation of spontaneous imbibition at a fine scale (single and multiple matrix block level), and assessing the validity of dual-medium simulation models, which will be further used to perform modelling at the full field scale. Some reservoir parameters were varied within plausible range to quantify their impact on the recovery mechanism. To mitigate the biases of dual-medium models, upscaling and pseudoisation techniques were applied to match the behaviour of explicit fine-scale single-porosity model. A particular emphasis on the modelling of salt diffusion is made through one-dimension model. It was found that, whereas pressure diffusion is rather well represented by the usual matrix-fracture exchange coefficient formalism, the underlying assumption of pseudo-steady state seems to be inappropriate for salt diffusion phenomenon. When salt diffusion is the main driver for low salinity water imbibition, for example at the early times of a switch from high salinity to low salinity, it appears that the salt diffusion process occurs in a transient regime that cannot be properly represented by the pseudo-steady state regime assumption. This has an impact on the modelled incremental recovery and consequently on the low salinity flooding efficiency evaluation.