Production of ultra-heavy oils is economically and technically challenging due to the very high viscosity of heavy oils, sharp viscosity increase over a small temperature drop and high operating costs. Reservoir oil can't even be mobilized by steam stimulation only due to inadequate reservoir energy. Even after the oils flow to the wellbore, the viscosity of the oils may exponentially increase when transported towards the wellhead due to the geothermal temperature decrease. The liquid oil could naturally turn into solid bitumen at any point where the temperature drops. The longer the travelling distance to surface for the oil, the bigger temperature drop, the greater the oil viscosity, and the more severe production challenges.
This paper presents the challenges associated with the production of ultra heavy oil in deep reservoirs in China. Operational difficulties widely exist in mobilization of in-situ oil, flow of oil from formation to wellbore, lifting of produced fluids from wellbore to surface, and surface processing and transportation of hydrocarbons. The sandstone reservoirs, sitting at a depth from 1600 to 1800 meters and having no support of any aquifer, contain approximate 4 million metric tons of 1.02~1.05g/cm3 heavy oil reserve. The oil-bearing formations have an average porosity of 27~29%, an average permeability of 1 Darcy and an original reservoir pressure of 16~17.5MPa. The oil viscosity at reservoir conditions (80°C) ranges from 6000 to 10000 centipoises (cP). Always keeping oil at a relatively low viscosity for feasible pumping is the theme topic with the thermal oil production in this type of reservoirs.
To find fit-for-purpose solutions, challenges had been analyzed in details for each part of the entire oil producing process covering the oil flow from the reservoirs to surface. The oil viscosity change with temperatures, the impact of oil viscosity reducers on the mobility of oil compounded with steam stimulation and CO2 injection for providing the initial energy to mobilize the heated oil, optimization of horizontal wells, screening of suitable wellbore lifting technology including wellbore heating and insulation and suitable chemicals for reducing the oil-water interfacial tension, and the steam stimulation optimization had been studied carefully prior to well drilling.
So far, 26 horizontal wells were drilled with an average of 130 meters horizontal section. Production data showed daily liquid rates at 800 tons at 55% water cut for all 26 producers after one year. The average peak oil production, the average cycle oil production capacity, the average cycle cumulative oil production of a single well was 25 metric tons per day, 14 metric tons per day and 2130 metric tons respectively. The average oil-steam ratio was 1.46 with a maximum oil-steam ratio of 5.26. The technologies discussed in this paper had been proved effective to produce ultra heavy oil from 1600 to 1800 meters formations with oil viscosity at 50°C conditions ranging from 180,000 to 260,000 cP.
EXPLORATION OF DEEP BASIN GAS POOL IN THE ORDOS BASIN Ma Xinhua & Ma Xinhua, graduated from Jianghan Petroleum Institute in 1982. Vice-president, professor- Cheng Mengjin ranking senior engineer of RIPED-Langfang under CNPC. No.44 Post Box, Langfang, Hebei, P.R. China Classified number P.C.: 065007 Abstract The Carboniferous-Permian System of the upper Paleozoic in Ordos Basin is a set of sedimentary formation with wide-coverage coal series. The gas-bearing reservoir is a set of compact sandstone with low porosity and permeability, of which the average porosity is less than 8%; and the permeability is less than 0.42×103mm2. The hydrocarbon source rock of coal series is in the period of high maturityover mature wet gaslot of dry gas generation, the gas generation amount coming to 539.83×1012m3. Through the research of the gas-water relations and the pressure features as well as exploration experiences, we determine that there exists the obvious phenomenon of gas-water inversion in the Carboniferous-Permian System of the upper Paleozoic, in the section of P2h8P1S2, from south to north, develops large areas of deep basin gas pool. Yet, after the Yanshanian Movement, with the rising of east part of the Ordos Basin, the deep basin gas pool lies in a reconstructive state now. Meanwhile, the speed of the hydrocarbon generation out of the source rock slowed down greatly. Although there is the supply of the desorption gas from coal-bearing rock, the amount is likely less than the lost, which made the early boundary of gas-water shrink back toward south. It is predicted that the distribution range of the deep basin gas in Ordos Basin will get to 12×104km2, and the prospect total resource amount exceeds 42.27×1012m3, and the current resource amount exceeds 4.27×1012m3. Introduction Deep basin gas pool refers to the gas accumulation developed in the downdip of structure in basin, and gas source rock connects with compact reservoirs. Generally, it has the following features: (1) Lie in center or deeper location of a basin; (2) Reservoirs are compact; (3) Gas-water inversion; (4) Mainly develop from the coal series formation; (5) Large scale reserves etc. Deep basin gas pool is a kind of unconventional natural gas pool, which has broadened the thought for exploration and the fields of gas exploration. Ordos Basin lies in the middle of China, of which geological structure characteristic is noted for the steady and the uniformity. Its integrated ups and downs, wide and gentle slope, weak anticline, horizontal formation and contiguity conformity are well known all of world. Hardly are there fractures and folds that will bring complex geological situation. The structure is favorable for oil/gas generation and preservation, which is one of the basic conditions of forming deep basin gas. On the broad gentle slope in Shanbei, the dip of formation in Carboniferous-Permian Period is low (<1o), and the average slope descending rate is only1/100. There isn't
Masters, C. D. (US Geological Survey, USA) | Attanasi, E. D. (US Geological Survey, USA) | Dietzman, W. D. (Energy Information Administration, USA) | Meyer, R. F. (US Geological Survey, USA) | Mitchell, R. W. (BP Canada Inc., Canada) | Root, D. H. (US Geological Survey, USA)
WORLD RESOURCES OF CRUDE OIL, NATURAL GAS, NATURAL BITUMEN, AND SHALE OIL Charles D. Masters, US Geological Survey, Reston, Virginia, USA; Emd D. Attanasi, US Geological Survey, Reston, Virginia, USA; William D. Dietzman, Energy Information Administration, Dallas, Texas, USA; Richard F. Meyer, US Geological Survey, Reston, Virginia, USA; Robert W. Mitchell, BP Canada, Inc., Calgary, Alberta, Canada; David H. Root, US Geological Survey, Reston, Virginia, USA. Abstract. The Ultimate Resources of world petroleum are assessed in about the same quantities and distributed broadly in the same areas as was reported to the Ilth World Petroleum Congress. The assessment as of 1/1/85, for the 12th World Petroleum Congress is: Oil (BBO) Gas (TCF) NGL (BB) Cumulative production 524 1173 Undiscovered resources Identified reserves 795 3908 59 95% 262 2650 Mode 425 4199 63 5 %o 927 8591 Ultimate resources 1744 9280 Two of the component parts of the assessment of Ultimate Resources of crude oil-the Original Reserves and the Undiscovered Resources-were compensatingly altered in this assessment by about 150 billion barrels (24 Gm3); the Original Reserves were increased and the Undiscovered Resources decreased. The reserves change reflects, heretofore uncounted, additions to reserves owing primarily to concepts of field growth. Including the field growth projections, it appears that world discovery over the past decade has been slightly less than production. The change in Undiscovered Resources derives in large part from a clearer understanding of the geologic limits to resource occurrence in the USSR and in Mexico, and from exploration failures in several key areas in the United States. Though the natural gas assessment remains substantially the same, there appears to be evidence of substantial under-reporting of gas resources owing to market immaturity. Assessments of heavy and extra-heavy crude oils, natural bitumens, and shale oil from oil shale remain reasonably consistent with past reports but economic reserves of these unconventional resources have increased owing to the expansion of commercial recovery projects. The distribution of conventional oil and gas is very strongly concentrated in the Eastern hemisphere while the world's unconventional resources are most prominent in the Western Hemisphere-notably in Venezuela and in Canada. Though ultimately only 25% of the world's oil will have been discovered offshore, 45% of the remaining Undiscovered Resource is assessed to be offshore. Natural gas also remains highly imbalanced in its distribution and, in addition, its production is imbalanced relative to the reserves distribution; the Middle East gas reserves are one of the largest underutilized energy resources in the world. Undiscovered Resources of gas are mainly concentrated in areas of large Original Reserves but assessed occurrences in the frontier Barents Sea likely will exceed 300 TCF (8.5 Tm3) and in the Niger delt