The collapse in natural gas prices shouldn’t have an outsized impact on the upstream master limited partnerships (MLP) in the model Portfolios, thanks to our preference for names with a liquids-weighted production mix and sizable hedge books.

With the prices of oil and natural gas liquids (NGL) still quite robust, many of our favorite producers continue to expand their output and grow their distributable cash flow. Some of our other favorites use future contracts to hedge their exposure to natural gas prices.

Aggressive Portfolio holding Linn Energy LLC (NSDQ: LINE) grew its first-quarter average daily production by a whopping 51 percent in the first quarter of 2011. Liquid hydrocarbons accounted for much of this growth.

During the quarter, the limited liability company (LLC) drilled three successful wells in the Granite Wash, an area that accounts for 40 percent of the firm’s 2012 capital expenditures.

Linn Energy has also announced $1.8 billion in acquisitions in recent months, including a joint venture with Anadarko Petroleum Corp (NYSE: APC) to use carbon dioxide to enhance production from a mature oil field in Wyoming.

Thanks to management’s policy of hedging the majority of production years in advance, Linn Energy’s average price realizations for natural gas came in at $6.33 per thousand cubic feet in the first quarter–well above prevailing prices.

Linn Energy has hedged 100 percent of its expected natural gas production through the end of 2017, protecting the firm’s cash flow from fluctuations in commodity prices for almost six years. The LLC has also hedged 100 percent of its oil production through 2015 and 70 percent of its NGL output over the next five years.

Although the firm’s production mix favors oil, management has shifted its acquisition strategy of late to acquire low-risk natural gas reserves at deep discounts that guarantee solid returns.

The proof of Linn Energy’s success is in its first-quarter bottom line. The company reported a headline earnings loss from hedges, which is irrelevant for MLPs. The best measure of profitability–distributable cash flow–increased by 43.8 percent from year-ago levels and covered Linn Energy’s recently boosted quarterly payout by a 1.14-to-1 margin.

Management expects the LLC to grow its production by 65 percent in 2012 and to generate enough cash flow to cover its distribution more than 1.2 times in the back half of the year. Yielding roughly 7.3 percent, units of Linn Energy LLC are a strong buy up to 40.

The other upstream operators in our model Portfolios–Legacy Reserves LP (NSDQ: LGCY), Mid-Con Energy Partners LP (NSDQ: MCEP) and Vanguard Natural Resources LLC (NYSE: VNR)–will report first-quarter numbers in the next few weeks. We’ll analyze these results in a series of Flash Alerts.

At this point, we expect this trio of upstream MLPs to post solid results, with little impact from natural gas prices. Recent news flow has been encouraging.

There’s no better guarantee that an MLP’s distribution is safe than when management raises the payout.

Legacy Reserves last week hiked its quarterly distribution to $0.555 per unit, up 0.9 percent sequentially and 4.7 percent on a year-over-year basis. Meanwhile, Vanguard Natural Resources in late April raised its quarterly payout to $0.5925 per unit, up roughly 4 percent from year-ago levels. Mid-Con Energy Partners, which went public in mid-December 2011, should also ramp up distribution growth in the coming year.

Legacy Reserves usually hedges about 65 percent to 75 percent of its anticipated annual production, which provides upside exposure to oil and NGL prices. In the fourth quarter of 2011, natural gas accounted for a mere 15.7 percent of the MLP’s revenue.

Oil accounts for 99 percent of Mid-Con Energy Partners’ production mix, making natural gas prices irrelevant to the firm’s profitability. That being said, the MLP has hedged about 75 percent of its anticipated 2012 output and 60 percent of its 2013 production.

Prior to its acquisition of Encore Energy Partners, oil, condensate and NGLs accounted for 66 percent of Vanguard Natural Resources’ proved reserves and 65 percent of 2011 production. The addition of Encore Energy Partners’ assets should increase the company’s liquids exposure.

In short, the upstream MLPs in our model Portfolios have little exposure to falling natural gas prices. Legacy Reserves LP rates a buy up to 32; Mid-Con Energy Partners LP is a buy up to 26.50; and Vanguard Natural Resources LLC is a buy up to 30.

The risks are higher outside the names in our model Portfolio. BreitBurn Energy Partners LP (NSDQ: BBEP) and QR Energy LP (NYSE: QRE) offer above-average yields and could be appealing bets for aggressive investors who are willing to take on additional risks.

Natural gas accounts for 55 percent of BreitBurn Energy Partners’ production mix, but management hedges production aggressively and recently assured unitholders that the MLP would grow its distribution by making acquisitions. To that end, the firm in late April announced the purchase of oil-producing properties in Wyoming that flow roughly 600 barrels per day.

BreitBurn Energy Partners has hiked its distribution for eight consecutive quarters, but we’ll be paying close attention when the MLP reports earnings on May 7.

QR Energy will report quarterly earnings on May 10, but management in early April hiked the distribution by 2.6 percent in a show of confidence. The MLP has sought to increase its exposure to liquids and closed the acquisition of Prize Petroleum LLC in late April. The firm has hedged 90 percent of its oil and gas output for 2012.

Investors should be aware that natural gas accounted for more than 50 percent of the firm’s production in the fourth quarter of 2011 and 23.7 percent of revenue. This outsized exposure to natural gas explains the stock’s elevated distribution yield of more than 10 percent. QR Energy LP is for aggressive investors only.