October 2011 ///
The North Urtabulak oil field in southern Uzbekistan was discovered in 1972, with 124.2 million bbl of calculated original oil in place. The field is a carbonate reef structure of Jurassic age, with average reservoir thickness of about 320 m (1,050 ft). To date, 119 wells have been drilled on the structure. A reservoir model in 2010 indicated significant volumes of oil in place, much of it trapped between existing wells. This situation was exacerbated by severe near-wellbore damage and pressure depletion in the reservoir. The operator, Tethys Petroleum, had previously implemented horizontal drilling, sidetracking and acid stimulation to access the remaining reserves, but these technologies were no longer considered cost-effective.
In selecting a drilling rig for the actual geological environment of well construction, a decision support system can reduce the cost per unit, construction time cycle and simplify the design complexity of the well.
While the Haynesville shale play offers great potential, it also poses significant challenges. The play is characterized by a network of fractures and faults, as well as very low permeability and high porosity that often result in over-pressurized zones. With depths ranging from 10,000 ft to 14,000 ft, the play also features significant high-pressure, high-temperature (HPHT) conditions that pose obstacles to drilling. The high cost of drilling and completing wells in the Haynesville shale presents a particularly difficult challenge to total well economics. Marginal gas prices, drilling hazards, related non-productive time (NPT), and varying initial production rates and decline rates further challenge the economics faced by operators working in the region.
Advances in new drill bit technology moved at an accelerating pace in the past year, as engineers continued to design bits to drill larger, higher-quality holes with better rates of penetration and more control. Shale is still on operators’ minds, and PDC bits are still the tool of choice.
Relative permeability is one of the most uncertain terms in multiphase flow through porous media. Therefore, such a basic parameter must be well uderstood to provide confidence in reservoir simulations.
In a fractured reservoir, evaluation of relative permeability curves is complicated due to the nature of double porosity systems, where fractures develop a discontinuity in multiphase flow between adjacent matrix blocks. Fracture relative permeability is examined here with corresponding effects on fractured reservoir performance.
There is no question that sustained low prices for natural gas have taken their toll on the Haynesville shale play of northwestern Louisiana and East Texas. The number of rigs working in the Haynesville has fallen steadily during the past 15 months, and there are reasons to be concerned that activity could continue falling off.
In the wake of tougher regulations, many oil and gas companies have established or expanded risk management systems integrated company-wide, or enterprise risk management (ERM). Do such systems necessarily make companies better prepared to deal with low-likelihood, high-impact events?
The plug-and-perf system creates multiple hydraulic fractures in a horizontal well completed with a cemented casing/liner. This system combines elements of two common fracturing techniques: limited entry and segmented fracturing using bridge plugs. Commercially, these systems are offered and supported by several suppliers.
System description. Fracturing operations begin from the toe of the well and proceed toward the heel, Fig. 1. Each pumping stage is used for fracturing multiple clusters of perforations designed based on the limited-entry technique. The number of clusters is based on the injection rate, with details discussed later. The sequence of operational steps consists of setting the plug in the desired location within the horizontal well, perforating the clusters and pumping the treatment according to the design. After all pumping stages are complete, all the plugs are milled out, and the well is cleaned and put on production. Depending on requirements, there are a variety of plug types used in these completions, but they are all drillable/millable and usually made of special composite material.
As California entered a period of severe drought in 2008, the challenges of using thermal methods to extract heavy oil became compounded by the difficulty of securing freshwater sources from which to generate the high-quality steam that these methods require. In an effort to manage the crisis, then-Gov. Arnold Schwarzenegger proclaimed a state of emergency and enacted widespread water-conservation measures. The drought, which officially lasted until March 2011, impacted heavy oil fields in the state that rely on affordable fresh water to feed boilers in thermal techniques such as steamflooding and cyclic steam stimulation (CSS). Essentially, these thermal techniques involve the injection of steam into wells to heat the viscous oil to flowing temperatures. As the drought intensified in California, the prospect of feeding boilers with oilfield produced water instead was studied as an alternative.
The vast oil and gas reserves of the Middle East and North Africa (MENA) region have historically played a dominant role in the global economy, and today the region continues to be a primary exporter of oil and gas all over the world. The political turmoil of the past year has brought uncertain times to the region and fresh challenges to the oil and gas industry. Despite this, the MENA region has seen continued high levels of upstream activity, rewarded with discoveries being made and new fields coming onstream. Even with the emergence of new significant hydrocarbon plays in Brazil and Sub-Saharan Africa, the MENA region will continue playing a key role in world energy.
In its 87th year, the 2011 Annual Technical Conference and Exhibition (ATCE) of the Society of Petroleum Engineers (SPE) will focus on developing shale resources, particularly the special requirements in the Rocky Mountain Niobrara and Bakken shale formations.
To meet its production goals, including enhanced recovery from mature fields, Saudi Aramco has been dedicated to the development, support and early adoption of recovery- and economy-enhancing, risk-reducing technologies, including horizontal and multilateral drilling, smart completions and completions utilizing passive inflow-control devices. To drain new areas of producing reservoirs more economically, the company has joined other operators in drilling small-diameter, short-radius, lateral re-entries with maximum reservoir contact, as opposed to new wellbores.
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