Cao, L. (PetroChina Tarim Oilfield Co.) | Yang, X. (PetroChina Tarim Oilfield Co.) | Zhang, S. (China University of Petroleum) | Wang, H. (China University of Petroleum) | Wang, K. (PetroChina Tarim Oilfield Co.) | Liu, H. (PetroChina Tarim Oilfield Co.) | Zhao, J. (Jianghan Machinery Research Inst.)
Since the coal seam is soft with low permeability in China, the stimulation effect of vertical well hydraulic fracturing technology is limited while horizontal well fracturing has instable wellbore leading to wellbore collapsing. Therefore, floor horizontal well hydraulic fracturing technology is proposed, that is drilling in the floor sandstone and connecting the coal seam by hydraulic fractures. A test area has been undertaken in 3# coal seam, southern Qinshui Basin, to demonstrate this technology. Through optimizing the well path, borehole structure, fracturing designs, and fracture propagation performance, a set of treatments were developed and applied successfully. The result shows that drilling floor horizontal well along with minimum horizontal principle stress, applying U-type well structure, and designing fractures with 3 stages, 130m half fracture length and 30D·cm flow conductivity achieves better production performance.
Sun, Yongpeng (China University of Petroleum) | Dai, Caili (China University of Petroleum) | Fang, Yanchao (China University of Petroleum) | Sun, Xin (China University of Petroleum) | You, Qing (China University of Geosciences) | Wu, Yining (China University of Petroleum) | Zhao, Mingwei (China University of Petroleum) | Zhao, Guang (China University of Petroleum)
Tightoil poses huge reservoir in many countries. Due to the poor reservoir properties, such as nanometer to micrometer pores, low permeability, energy deficiency, the oil recovery in tightoil reservoir is very low, even with horizontal drilling and hydraulic fracturing. The small pores are featuring large capillary pressure thus spontaneous imbibition. Surfactant would accelerate this process. However, due to the small amount of oil in core, the accurate recording of oil recovery is challenging, especially during dynamic imbibition within fracture matrix system. Nuclear Magnetic Resonance (NMR) T2 spectra was used to characterized the migration of oil and water in pores and throats during dynamic imbibition. Various phenomenons are revealed and proved by T2 spectra figure, such as: water imbibed into small pores, oil expelled from large pores, and oil film formed on fracture face. The oil recovery during dynamic imbibition was examined online during experiment from the peak area generated by T2 spectra. Before and after the dynamic imbibition, Magnetic Resonance Imaging (MRI) was used to compare the saturation and distribution of oil in the core sample. When the oil drop migrates out of the pores, it will emerge from the surface of rock sample. Its shape on top, lateral, and bottom of the sample was observed with a long distance microscope. Their growth in width and height was compared carefully. The growth rate was categorized into different stages, and quantitatively compared.
Sukapradja, Aldyth (Total E&P Indonesie) | Herdianto, Roni (Total E&P Indonesie) | Clark, Jesse (Total E&P Indonesie) | Adam, Cepi (Total E&P Indonesie) | Ashari, Untung (Total E&P Indonesie) | Saragih, Baginda (Total E&P Indonesie) | Sitorus, Rio (Total E&P Indonesie) | Giriansyah, Bayu (Total E&P Indonesie)
Sisi-Nubi (SNB) is a gas field located 25 km offshore from the modern Mahakam delta with overpressure reservoirs being found typically in the Sisi Main Zone (SMZ) interval. SNB 3D seismic data indicates a velocity reversal in the SMZ interval, where the overpressure occurs. This velocity reversal has a relation with location of shelf break (distal area), where beyond shelf break the NTG value is sharply decreased.
In the Mahakam area, overpressure gas reservoirs are one of the main issues in terms of drilling hazards. This has been historically managed by integrating surrounding wells' pressure data to predict the pore pressure profile that would be expected in an upcoming well. In new areas or where pressure data is lacking, it is difficult to predict the PP which can result either in heavier than necessary well architectures or an increased risk of taking a kick.
An integrated pore pressure study has been carried out on the SNB field in order to provide three dimensional and spatially continuous pore pressure prediction using four different disciplines: sedimentology, reservoir geology, geophysics and geomechanics. The integrated pore pressure model over SNB is contained within a 3D geological model where the Eaton equation can be run using following datasets: sonic well data and sedimentological trend (Well Driven model), upscaled/resampled seismic interval velocity (seismic driven model) and hybrid method as compromise between two data sources involves using the seismic data as a soft trend for the extrapolated well data (hybrid model).
Based on the blind well test analysis, the hybrid methodology shows the best result in terms of precision and 3D distribution and allows a continuous prediction of pore pressures even where there is poor well control. However, the others two methodologies could be used as an alternative when the available data is limited.
This methodology gives a new approach with more integrated information in 3D pore pressure modeling that improved the classic pore pressure prediction in field Scale and/or basin scale. However, with the remaining uncertainty and discrepancy between the DT well scale velocity and the DT seismic velocity, and considering all detail well events important inputs (Gas evolution including long connection tests, kick, pressure test, HC bouyancy and other drilling events), collaboration with a strong 1D Pore Pressure synthesis will give a comprehensive result.
Commercial development of coalbed methane (CBM) in China has lasted for a decade. However, in 2015 annual CBM production in China was less than 5 Bcm and lagged far behind those in US (35 Bcm) and Australia (18 Bcm). In this paper, we review the published literature to determine the engineering challenges and opportunities of CBM production in China. Our review has identified seven major engineering challenges to CBM development in China. They are low cleat permeability and underpressured formation pressure of high-rank coals, ductility of coal seams, suboptimal fracturing fluids, formation damage during drilling, borehole instability in horizontal wells, frequent pump failures during production, and inadequate produced water treatment methods.
Each of these challenges provides an opportunity for improvement. We propose a refocus on low-rank coals which have higher permeability. Other opportunities include development of better hydraulic fracturing fluids, non-formation damaging drilling fluids, use of geomechanics to understand borehole instability, optimization of the artificial lift methods and more robust and environmentally friendly produced water treatment methods.
Recently in Indonesia are experiencing various of revision and improvement in the regulations, related with the oil and gas industry activity, this kind of situation certainly will impact to the investment atmosphere in the Indonesia oil and gas upstream. International Oil Company and the Government has different point of view related to contracts in PSC. Several analysis or study has been done by institutions and individuals through articles or papers on the comparing for the terms and conditions of a contract with different country. But not many have discussed particularly about the general change of PSC in Indonesia.
This study will compare the historical of Indonesia PSC generations from generation I (1966) until the recent fiscal terms of gross split (2017). Those terms will be compare by using a hypothetical block to modelize the PSC block in Indonesia, which consist of several field. Some assumption also will be used for each field with different peak rate, development scenario, capital variable cost ranges, operation variable cost ranges, which those range data are expected still within the range of most likely consist parameter for PSC block in Indonesia.
This study purpose is to analyze if the Gross Split mechanism is more attractive or equal the PSC Cost Recovery. The result of this study shown that the gross split PSC refer to the Minister of Energy and Mineral Resources no.52 year 2017 is still attractive to the investor from the contractor take perspective. Eventough with the PSC Cost Recovery mechanism the contractor feels more secure for the cost that can be recover from the oil and gas that produces, as part of cost recovery. If the application of Gross Split is clear enough from the regulation, tax, assets rent and others, surely this mechanism can attract more investor to do exploration and development in Indonesia.
Regardless of the political and strategic interests of the Indonesia government or the National Oil Company, the results of this study hopefully can be useful for the professional, educational institution, and government for lesson and learn. How the fiscal term can be impact to the government take, contractor take, cost recovery also the production target related with reserves replacement.
The Gas-Assisted Gravity Drainage (GAGD) process has been suggested to improve oil recovery in both secondary and tertiary recovery through immiscible and miscible injection modes. In contrast of Continuous Gas Injection (CGI) and Water-Alternative Gas (WAG), the GAGD process takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement and improve oil recovery. In the GAGD process, the gas is injected through vertical wells to formulate a gas cap to allow oil and water drain down to the horizontal producer (s). The GAGD process has been invented based on experimental work at Louisiana State University. Limited studies have been conducted to test its effectiveness in real oil field evaluations.
In this paper, a comprehensive literature review was presented to summarize all the references about the GAGD process concepts, principles, and field-scale evaluations. Particularly, the paper presents introduction about the gas injection approaches for Enhanced Oil recovery, the physical model description and evaluation of the GAGD Process Physical Model, the factors influencing the GAGD process in addition to review of all the field-scale evaluation studies. Moreover, the validation of the GAGD process in field-scale application was fully discussed with focusing the light on its weak points with respect to the optimal decision of application for maximum oil recovery. In one study, sensitivity analysis, production optimization, and uncertainty assessment have been also included and clarified in this paper.
The paper ended with field-scale compositional simulations of continuous and cyclic CO2 injection modes through the GAGD process in a heterogeneous sandstone oil reservoir in South Rumaila oil field. It was noticed the effectiveness of the GAGD process to improve oil recovery to promising levels. It was also concluded that cyclic GAGD process was much better than the continuous one for higher oil production, smaller gas injection, and smaller injection pressure.
Hai, Qu (Dong Chaoqun Chongqing University of Science & Technology) | Ying, Liu (Dong Chaoqun Chongqing University of Science & Technology) | Chuande, Zhou (Dong Chaoqun Chongqing University of Science & Technology) | Liancheng, Ren (Dong Chaoqun Chongqing University of Science & Technology) | Qinwen, Wei (Dong Chaoqun Chongqing University of Science & Technology) | Yancang, Lv (Sinopec International Petroleum Company) | Jun, Hou (Sinopec International Petroleum Company)
The Woodford shale in Oklahoma is an ultra-low permeability reservoir that must be effectively fracture stimulated for the development of shale oil. Hundreds of horizontal wells with 4000ft-5000ft lateral length were stimulated by hydraulic fracture technology. Several pilots with 9000ft lateral length were also tested to figure out the relationship between lateral length and outcome. The research found that the shape of manual fracturein Woodford(WDFD) formation is the most important factor affecting the production.
The wells were stimulated in stages with large hydraulic fracture treatments. However, production isn't directly related to the size of the stimulated volume. Microseismic mapping techniques, simulation method, post-production analysis and formationstress calculation are cooperated to study the characteristics of fracture extension. It is found that there are two kinds of fracture shape which are different from Barnett shale. This paper will test the effect of fracturing liquid and proppant on the fracture growth; The values of triaxial stresswere obtained in the neighboring layers and WDFD formation; Finally, the pilot wellisan example to illuminate fracture extension.
Understanding fracture growth in the Woodford shale will enhance the development of the play by helping operators optimize fracture completion and well placement strategies.
AB field has undergone secondary recovery of water injection for pressure support and sweep efficiency improvement. From proactive surveillance program, it was further discovered that AB field performance is improving without water injection. Pilot shut-in water injection study initially commenced post 5 years of production. From the pilot water injection shut-in, surveillance data was used for thorough analysis to conclude that secondary recovery through water injection will reduce field recovery due to early water out coupled with moderate to strong aquifer strength.
Close pressure monitoring, surveillance database, and other diagnostic plots used to gauge the water injection healthiness in AB field. Reservoir modelling was built to validate the implication of water injection secondary recovery to the field. Complete surveillance data and gathering method will be presented in this paper to permit readers to replicate the analysis prior to conclude secondary recovery type of mechanism, typically water injection, is beneficial to the field or proven otherwise.
Pilot shut-in water injection has proven the following: (1) It was observed that AB field pressure still maintains above the pressure target of initial Field Development Study, (2) Watercut performance has significantly increased post pilot water injection shut-in, (3) no substantial impact on the reserves loss, while in contrast, water injection stoping will improve recovery due to delaying the wells watered out time. For this marginal field of AB, an incremental of 0.8-1.7 MMstb reserves recovery will contribute to higher recovery factor. This is also due to the moderate to strong aquifer strength against weak to moderate aquifer strength anticipated earlier in FDP.
Casehole contact logging was conducted at two wells in the field to monitor the contact movement. From all the observation and analysis conducted, AB field was further optimize by the Reservoir Management Plan (RMP) revision. Lesson learned from the case study will enhance others' understanding and view prior to deciding on secondary recovery method to any field. RMP study should be updated as the production continues and once more data is acquired from the right surveillance program.
Acoustic Induced Vibration (AIV) refers to the high acoustic energy generated by pressure-reducing devices that excite pipe shell vibration modes, producing excessive dynamic stress. Analysis of this risk is an important part of Asset Integrity Management systems as AIV can cause catastrophic piping failure. Existing guidelines address this risk through an analytical assessment. However, these methodologies are not fully known and input parameters are limited. Some limits to the guidelines are pointed out with recommendations to improve them.
The approach presented for identifying AIV damage is based on a dynamic stress evaluation at pipe discontinuities (welded connections and supports). This evaluation is performed through a fluid-structure coupling Finite Element Analysis. Pressure fluctuations inside the pipe are predicted and coupled with a pipe structural analysis. This methodology is provided with its validation through measurement on an actual AIV field case, corresponding to a crack initiation due to AIV on a FPSO flare network tail pipe.
To conclude the paper, the method is then applied to quantitatively assess the mitigation actions' efficiency base on an actual case. Different solutions have been tested individually to end up with a final solution that reduces the damage to acceptable levels in the most cost-effective manner.
The sources of this high acoustic energy are pressure-reducing devices (valves, restricted orifices…) with high pressure drop and important mass flow rate. In such devices, the amount of energy dissipated is quite high, although most of the energy is converted to heat but there is still a significant part converted to sound or pressure waves that will excite the pipe wall. This broadband and high-frequency excitation propagates through the pipe, amplified by transverse acoustic pipe modes which later excite the pipe's shell vibration mode. While running along straight pipes, the impact of vibration is limited due to axisymmetry of the pipe shell mode shape. However, when the excitation comes to a non-axisymmetrical discontinuity (branch, small bore, support…), vibrations are amplified, leading to high dynamic stress that can cause pipe fatigue failure. As these vibrations occur at high frequencies, i.e. with a high fatigue cycle rate, fatigue failure occurs within a few minutes to a few hours.
(a) Fluid Acoustic mode; (b) Pipe shell mode.
(a) Fluid Acoustic mode; (b) Pipe shell mode.
For offshore plant, the major risk associated with this phenomenon is related to flare systems. Blowdown valves, restricted orifices and pressure safety valves in these systems usually encounter large pressure drops and important mass flow rates. As the acoustic energy generated by these devices propagates downstream with small attenuation, the whole flare network is affected by the risk of AIV failure. Flare systems are gas associated systems and they are safety-related, potential pipe failure could lead to catastrophic consequences. Therefore, assessing and controlling the AIV risk is an essential part of Asset Integrity Management.
AIV has been an on-going research subject since initial publications in the late 70s and methodologies have been developed to help engineers to assess this risk. The dominant methodology for the Oil & Gas industry is published by the Energy Institute. In Energy Institute guidelines address the AIV risk through an analytical assessment methodology. It is very efficient in performing a quick screening for large numbers of pipes. However, when it comes to mitigation measures, the limited number of input parameters used to quantify the Likelihood of Failure (LOF) reduces the range of possible mitigation measures. Since the efficiency of certain mitigation measures are not LOF calculation parameters and therefore cannot be assessed.
To overcome this limitation, a new detailed Finite Element methodology has been developed using the coupling between fluid and structure, making it possible to predict dynamic stress for complex piping models. This methodology will be introduced in the next chapter, including a validation through measurements on actual AIV field case.
Using this methodology, different AIV mitigation actions (such as: the use of sweepolets, forged tees, full encirclement supports, full encirclement wrap branch reinforcements) that not included in the scopes of Energy Institute guidelines are assessed. Comparison between computation results with and without mitigation measures makes it possible to quantify the impact of such modifications accurately and to establish a LOF adjustment coefficient when using these modifications.
This paper describes an efficient approach to evaluate waterflood connectivity performance in complex compartmentalized reservoir, the objectives are to increase the oil production performance and manage mature fields effectively, and also to enhance ultimate recovery in the long run. It is also very useful to get better understanding of detail reservoir characterization, reservoir internal architecture, reservoir distribution, pressure monitoring and subsequent water flood sweep pattern efficiency. Multi-disciplinary methods applied to maximizing all of data and create strong analysis. The first phase is deep sub-surface analysis in property distribution, simultaneous inversion, 4D time lapse seismic and sweep pattern analysis, those analysis have been done to get comprehensive interpretation of reservoir characterization and waterflood monitoring. The second phase is tracer injection, we implement tracer in several wells to ensure connectivity from injector to several producers are efficient and optimal. These methods were performed for several regions of this area which contains a large number of well, nearly 200 wells consist of vertical, deviated and horizontal wells. Reservoir distribution in Windri area interpreted as stacking channel with high sinuosity geometry. This reservoir consists of predominantly of marginal marine claystone interbedded with deltaic sandstones, thin limestone and coal. Bio-stratigraphic analysis from cores shows that the reservoir was deposited in estuarine setting, interrupted by a brief shallow marine incursion. Seismic amplitude mapping at the upper base Gita horizon reveals a system of meandering channels. Compartmentalised reservoir in Windri area divided into 5 sweep pattern to make analysis more detail and accurate. Each of compartment have different characteristic, this is the challenging part in Windri area. East of windri area channel divided into 4 channels and it shows the evolution and movement of the channel that can control the property distribution and reservoir connectivity. Group two shows good result from tracer injection and it is supporting the interpretation of reservoir distribution and characterization within the area. Integrated 4D time lapse seismic generate pressure monitoring movement from each of waterflood phase. The results of this integrated study implementation are excellent, the ineffective water injection pattern now become effective, there is no unavailing injection well, every pattern is connected and link to each other, so that we can achieve our goal to enhanced recovery factor from 16% to 20%. Reservoir characterization using multi-discipline method reduce uncertainty of heteroginity sand and fluid prediction. Integrated waterflood analysis has been implemented for prospect generation, production optimization and overcome pressure degredation in this area.